This is difference between the default preference of Firefox 71.0 beta 6 and one of 70.0.1. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 70.0.1Firefox 71.0 beta 6
accessibility.heading-element-level-changes.enabled undefined false
app.productInfo.baseURL https://www.mozilla.org/firefox/features/ 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
apz.axis_lock.breakout_angle 0.3926991 0.392699
apz.axis_lock.direct_pan_angle 1.047197 1.0472
apz.axis_lock.lock_angle 0.5235987 0.523599
apz.fling_curve_function_x1 0 0.0
apz.fling_curve_function_x2 1 1.0
apz.fling_curve_function_y1 0 0.0
apz.fling_curve_function_y2 1 1.0
apz.pinch_lock.scoll_lock_threshold 0.03125 undefined
browser.cache.offline.insecure.enable false undefined
browser.cache.offline.storage.enable undefined false
browser.contentblocking.cfr-milestone.enabled undefined true
browser.contentblocking.cfr-milestone.milestone-achieved undefined 0
browser.contentblocking.cfr-milestone.milestones undefined [1000, 5000, 10000, 25000, 50000, 100000, 500000]
browser.display.permit_backplate undefined true
browser.newtabpage.activity-stream.asrouter.useRemoteL10n undefined true
browser.newtabpage.activity-stream.discoverystream.campaign.blocks undefined {}
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.offline-apps.notify true undefined
browser.search.separatePrivateDefault.ui.banner.max undefined 0
browser.search.separatePrivateDefault.ui.enabled undefined false
browser.search.suggest.enabled.private undefined false
browser.tabs.documentchannel undefined false
browser.tabs.remote.separatedMozillaDomains addons.mozilla.org,accounts.firefox.com addons.cdn.mozilla.net,addons.mozilla.org,accounts.firefox.com
devtools.browserconsole.input.editor undefined false
devtools.connectpage.enabled false undefined
devtools.debugger.features.inline-preview false true
devtools.debugger.features.overlay undefined true
devtools.debugger.features.overlay-step-buttons false undefined
devtools.debugger.features.watchpoints undefined false
devtools.debugger.log-event-breakpoints undefined false
devtools.inspector.compatibility.enabled undefined false
devtools.inspector.use-new-box-model-highlighter undefined false
devtools.layout.flex-container.opened undefined true
devtools.layout.flex-item.opened undefined true
devtools.netmonitor.features.requestBlocking undefined false
devtools.responsive.browserUI.enabled undefined false
devtools.responsive.show-setting-tooltip true undefined
devtools.target-switching.enabled undefined false
devtools.webconsole.features.editor false undefined
devtools.webide.autoConnectRuntime true undefined
devtools.webide.autoinstallADBExtension true undefined
devtools.webide.busyTimeout 10000 undefined
devtools.webide.enableLocalRuntime false undefined
devtools.webide.enabled false undefined
devtools.webide.lastConnectedRuntime undefined
devtools.webide.lastSelectedProject undefined
devtools.webide.restoreLastProject true undefined
devtools.webide.templatesURL https://code.cdn.mozilla.net/templates/list.json undefined
devtools.webide.zoom 1 undefined
dom.datatransfer.mozAtAPIs true false
dom.disable_window_showModalDialog true undefined
dom.event.handling-user-input-time-limit 1000 undefined
dom.formdata.event.enabled undefined false
dom.media.mediasession.enabled undefined false
dom.missing_prop_counters.enabled undefined false
dom.postMessage.sharedArrayBuffer.withCOOP_COEP undefined false
dom.security.respect_document_nosniff false true
dom.storage.next_gen false true
dom.targetBlankNoOpener.enabled false true
dom.user_activation.transient.timeout undefined 5000
dom.webnotifications.requireuserinteraction false true
dom.webshare.enabled undefined false
dom.xmldocument.async.enabled false undefined
dom.xmldocument.load.enabled false undefined
extensions.abuseReport.amWebAPI.enabled undefined false
extensions.abuseReport.amoDetailsURL undefined https://services.addons.mozilla.org/api/v4/addons/addon/
extensions.abuseReport.openDialog undefined false
extensions.abuseReport.url https://addons.mozilla.org/api/v4/abuse/report/addon/ https://services.addons.mozilla.org/api/v4/abuse/report/addon/
extensions.cookiesBehavior.overrideOnTopLevel false undefined
extensions.webcompat-reporter.enabled false true
first-startup.timeout undefined 30000
general.aboutConfig.enable undefined true
general.useragent.site_specific_overrides true undefined
general.warnOnAboutConfig true undefined
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.direct3d11.use-double-buffering false true
gfx.webrender.debug.obscure-images undefined false
gfx.webrender.debug.smart-profiler undefined false
gfx.webrender.start-debug-server false undefined
identity.sendtabpromo.url undefined https://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/send-tab
idle_period.cross_process_scheduling undefined true
image.mem.surfacecache.max_size_kb 1048576 2072576
javascript.options.main_thread_stack_quota_cap undefined 2097152
javascript.options.wasm_trustedprincipals undefined true
layers.effect.contrast 0 0.0
layers.low-precision-opacity 1 1.0
layout.accessiblecaret.height 36 36.0
layout.accessiblecaret.width 34 34.0
layout.css.clip-path-path.enabled false true
layout.css.column-span.enabled false true
layout.css.devPixelsPerPx -1 -1.0
layout.css.grid-template-subgrid-value.enabled false true
layout.css.line-height.normal-as-resolved-value.enabled false true
layout.css.moz-document.url-prefix-hack.enabled true false
layout.css.moz-touch-enabled.enabled undefined true
layout.css.prefixes.device-pixel-ratio-webkit true undefined
layout.css.scroll-anchoring.suppressions.enabled undefined true
layout.css.scroll-snap-v1.enabled true undefined
layout.css.scroll-snap.enabled false undefined
layout.css.scroll-snap.prediction-sensitivity 0.750 0.75
layout.css.width-and-height-map-to-aspect-ratio.enabled false true
layout.css.xul-box-display-values.survive-blockification.enabled undefined true
layout.dynamic-reflow-roots.enabled false true
layout.scroll.root-frame-containers false undefined
mathml.deprecated_alignment_attributes.disabled undefined false
mathml.deprecated_menclose_notation_radical.disabled undefined false
mathml.mfenced_element.disabled undefined false
mathml.mfrac_bevelled_attribute.disabled undefined false
mathml.script_shift_attributes.disabled undefined false
mathml.xlink.disabled undefined false
media.ffvpx.mp3.enabled undefined true
media.hardwaremediakeys.enabled undefined false
media.peerconnection.dtls.version.max undefined 771
media.peerconnection.dtls.version.min undefined 770
media.webrtc.hw.h264.enabled undefined false
network.delay.tracking.load 0 undefined
network.notify.dnsSuffixList undefined true
network.trr.builtin-excluded-domains undefined localhost,local
network.trr.clear-cache-on-pref-change undefined true
network.trr.excluded-domains localhost,local
network.warnOnAboutNetworking false undefined
offline-apps.allow_by_default true undefined
offline-apps.quota.warn 51200 undefined
permissions.delegation.enable undefined false
permissions.desktop-notification.postPrompt.enabled false true
plugins.load_appdir_plugins false undefined
privacy.annotate_channels.strict_list.enabled false true
privacy.socialtracking.notification.counter 0 undefined
privacy.socialtracking.notification.enabled true undefined
privacy.socialtracking.notification.lastShown 0 undefined
privacy.socialtracking.notification.max 2 undefined
privacy.socialtracking.notification.period.min 172800000 undefined
privacy.socialtracking.notification.session.pageload.min 4 undefined
privacy.trackingprotection.fingerprinting.enabled false true
security.aboutcertificate.enabled false true
security.block_Worker_with_wrong_mime false true
security.csp.enableNavigateTo undefined false
security.disallow_non_local_systemprincipal_in_tests undefined false
security.ssl.errorReporting.enabled true false
security.tls.version.enable-deprecated undefined false
services.sync.engine.bookmarks.buffer false true
services.sync.engine.bookmarks.validation.enabled undefined true
services.sync.engine.passwords.validation.enabled undefined true
services.sync.fxa.privacyURL https://accounts.firefox.com/legal/privacy undefined
services.sync.fxa.termsURL https://accounts.firefox.com/legal/terms undefined
signon.includeOtherSubdomainsInLookup false true
signon.management.page.sort undefined name
signon.showAutoCompleteOrigins false true
toolkit.telemetry.enabled false true
toolkit.telemetry.testing.overrideProductsCheck undefined false
trailhead.firstrun.branches join-supercharge
widget.content.gtk-theme-override undefined