This is difference between the default preference of Firefox 72.0 beta 3 and one of 71.0. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 71.0Firefox 72.0 beta 3
accessibility.heading-element-level-changes.enabled false undefined
app.releaseNotesURL https://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=whatsnew https://www.mozilla.org/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=whatsnew
app.update.channel release beta
app.update.url.details https://www.mozilla.org/%LOCALE%/firefox/notes https://www.mozilla.org/%LOCALE%/firefox/beta/notes
app.update.url.manual https://www.mozilla.org/firefox/ https://www.mozilla.org/firefox/beta
browser.bookmarks.editDialog.maxRecentFolders undefined 7
browser.cache.offline.storage.enable true false
browser.display.permit_backplate false true
browser.messaging-system.personalized-cfr.score-threshold undefined 5000
browser.messaging-system.personalized-cfr.scores undefined {}
browser.newtabpage.activity-stream.asrouter.providers.whats-new-panel {"id":"whats-new-panel","enabled":true,"type":"remote-settings","bucket":"whats-new-panel","updateCycleInMs":3600000,"exclude":["EXTENDED_TRIPLETS_PRETRAILHEAD"]} {"id":"whats-new-panel","enabled":true,"type":"remote-settings","bucket":"whats-new-panel","updateCycleInMs":3600000}
browser.newtabpage.activity-stream.discoverystream.campaign.blocks {} undefined
browser.newtabpage.activity-stream.discoverystream.flight.blocks undefined {}
browser.newtabpage.activity-stream.discoverystream.lang-layout-config undefined en
browser.newtabpage.activity-stream.telemetry.ping.endpoint https://tiles.services.mozilla.com/v4/links/activity-stream undefined
browser.newtabpage.activity-stream.telemetry.structuredIngestion.endpoint https://incoming.telemetry.mozilla.org/submit/activity-stream https://incoming.telemetry.mozilla.org/submit
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.ping-centre.production.endpoint https://tiles.services.mozilla.com/v3/links/ping-centre undefined
browser.ping-centre.staging.endpoint https://onyx_tiles.stage.mozaws.net/v3/links/ping-centre undefined
browser.search.modernConfig undefined false
browser.tabs.remote.dataUriInDefaultWebProcess undefined false
browser.urlbar.megabar false undefined
browser.urlbar.timesBeforeHidingSuggestionsHint 4 undefined
browser.urlbar.update1 undefined false
browser.urlbar.update1.expandTextOnFocus undefined false
browser.urlbar.update1.view.stripHttps undefined false
browser.urlbar.userMadeSearchSuggestionsChoice false undefined
devtools.command-button-scratchpad.enabled false undefined
devtools.debugger.features.windowless-service-workers undefined false
devtools.inspector.color-scheme-simulation.enabled undefined false
devtools.performance.recording.duration undefined 0
devtools.performance.recording.entries undefined 10000000
devtools.performance.recording.features undefined ["js","leaf","stackwalk"]
devtools.performance.recording.interval undefined 1000
devtools.performance.recording.threads undefined ["GeckoMain","Compositor","Renderer"]
devtools.recordreplay.enabled undefined false
devtools.recordreplay.fastLogpoints undefined false
devtools.responsive.metaViewport.enabled false true
devtools.scratchpad.editorFontSize 12 undefined
devtools.scratchpad.enableAutocompletion true undefined
devtools.scratchpad.enabled false undefined
devtools.scratchpad.lineNumbers true undefined
devtools.scratchpad.recentFilesMax 10 undefined
devtools.scratchpad.showTrailingSpace false undefined
devtools.scratchpad.wrapText false undefined
docshell.shistory.testing.bfevict undefined false
dom.formdata.event.enabled false true
dom.indexedDB.enabled true undefined
dom.ipc.plugins.allow_dxgi_surface undefined true
dom.mozPaintCount.enabled undefined false
dom.postMessage.sharedArrayBuffer.bypassCOOP_COEP.insecure.enabled undefined false
dom.promise_rejection_events.enabled true undefined
dom.security.respect_document_nosniff false true
dom.storage.next_gen false true
dom.targetBlankNoOpener.enabled false true
dom.vr.webxr.enabled undefined false
dom.webcomponents.elementInternals.enabled undefined false
dom.webnotifications.requireuserinteraction false true
dom.webshare.requireinteraction undefined true
extensions.blocklist.useXML undefined false
extensions.content_script_csp.enabled undefined false
extensions.content_script_csp.report_only undefined true
extensions.contentblocker.enabled undefined false
extensions.webcompat-reporter.enabled false true
fission.sessionHistoryInParent undefined false
font.cjk_pref_fallback_order undefined zh-cn,zh-hk,zh-tw,ja,ko
geo.wifi.uri https://www.googleapis.com/geolocation/v1/geolocate?key=%GOOGLE_LOCATION_SERVICE_API_KEY% https://location.services.mozilla.com/v1/geolocate?key=%MOZILLA_API_KEY%
gfx.compositor.glcontext.opaque false undefined
gfx.core-animation.enabled false undefined
gfx.core-animation.tint-opaque undefined false
gfx.direct3d11.use-double-buffering false true
gfx.webrender.compositor undefined false
gfx.webrender.compositor.max_update_rects undefined 0
gfx.webrender.debug.glyph-flashing undefined false
gfx.webrender.enable-gpu-markers undefined false
gfx.webrender.max-partial-present-rects undefined 0
gl.require-hardware false undefined
javascript.options.writable_streams undefined false
layers.advanced.fission.enabled undefined false
layout.css.always-repaint-on-unvisited undefined false
layout.css.individual-transform.enabled false true
layout.css.motion-path-ray.enabled undefined false
layout.css.motion-path.enabled false true
layout.css.moz-binding.content.enabled false undefined
layout.css.moz-document.url-prefix-hack.enabled true false
layout.css.notify-of-unvisited undefined false
layout.css.scroll-anchoring.max-consecutive-adjustments undefined 10
layout.css.scroll-anchoring.min-average-adjustment-threshold undefined 3
layout.css.shadow-parts.enabled false true
layout.css.zoom-transform-hack.enabled undefined false
layout.dynamic-reflow-roots.enabled false true
layout.viewport_contains_no_contents_area false true
media.geckoview.autoplay.request undefined false
media.geckoview.autoplay.request.testing undefined 0
media.peerconnection.ice.obfuscate_host_addresses false true
media.peerconnection.ice.obfuscate_host_addresses.whitelist undefined
media.peerconnection.sdp.alternate_parse_mode undefined never
media.peerconnection.sdp.parser undefined sipcc
media.peerconnection.sdp.rust.compare false undefined
media.peerconnection.sdp.rust.enabled false undefined
media.rdd-webaudio.batch.size undefined 100
media.videocontrols.picture-in-picture.audio-toggle.enabled undefined false
media.videocontrols.picture-in-picture.enabled false true
media.videocontrols.picture-in-picture.video-toggle.enabled false true
mousewheel.ignore_cursor_position_in_lparam undefined false
network.http.http3.default-max-stream-blocked undefined 10
network.http.http3.default-qpack-table-size undefined 65536
network.http.http3.enabled undefined false
network.netlink.route.check.IPv4 23.219.91.27 undefined
network.netlink.route.check.IPv6 2a02:26f0:40::17db:5b1b undefined
network.notify.checkForNRPT undefined true
network.notify.checkForProxies undefined true
network.preload-experimental undefined false
network.trr.enable_when_nrpt_detected undefined false
network.trr.enable_when_proxy_detected undefined false
network.trr.enable_when_vpn_detected undefined false
network.trr.send_accept-language_headers undefined false
permissions.desktop-notification.postPrompt.enabled false true
permissions.isolateBy.privateBrowsing undefined true
permissions.isolateBy.userContext undefined false
plugin.defaultXpi.state 2 undefined
privacy.annotate_channels.strict_list.enabled false true
privacy.restrict3rdpartystorage.heuristic.opened_window_after_interaction undefined true
privacy.restrict3rdpartystorage.heuristic.window_open undefined true
privacy.trackingprotection.fingerprinting.enabled false true
security.block_Worker_with_wrong_mime false true
security.cert_pinning.hpkp.enabled undefined false
security.disallow_non_local_systemprincipal_in_tests undefined false
security.osclientcerts.autoload undefined false
security.remote_settings.intermediates.enabled false true
security.tls.hello_downgrade_check false true
services.sync.engine.bookmarks.buffer false true
services.sync.engine.bookmarks.validation.enabled undefined true
services.sync.engine.passwords.validation.enabled undefined true
signon.management.page.showPasswordSyncNotification undefined true
signon.storeSignons undefined true
svg.text-spacing.enabled undefined false
toolkit.telemetry.enabled false true
toolkit.telemetry.hybridContent.enabled true undefined
urlclassifier.features.socialtracking.annotate.blacklistTables social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256 social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256
urlclassifier.features.socialtracking.blacklistTables social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256 social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256
urlclassifier.trackingTable moztest-track-simple,base-track-digest256 moztest-track-simple,ads-track-digest256,social-track-digest256,analytics-track-digest256
webgl.cgl.multithreaded undefined true
widget.disable-dark-scrollbar undefined false
widget.wayland_vsync.enabled undefined false