This is difference between the default preference of Firefox 73.0 beta 3 and one of 72.0.1. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 72.0.1Firefox 73.0 beta 3
app.normandy.last_seen_buildid undefined
app.normandy.onsync_skew_sec undefined 600
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.cache.offline.storage.enable true false
browser.display.permit_backplate false true
browser.messaging-system.fxatoolbarbadge.enabled true undefined
browser.newtabpage.activity-stream.asrouter.providers.cfr-fxa {"id":"cfr-fxa","enabled":true,"type":"remote-settings","bucket":"cfr-fxa","frequency":{"custom":[{"period":"daily","cap":1}]}} {"id":"cfr-fxa","enabled":true,"type":"remote-settings","bucket":"cfr-fxa","frequency":{"custom":[{"period":"daily","cap":1}]},"updateCycleInMs":3600000}
browser.newtabpage.activity-stream.asrouter.providers.message-groups undefined {"id":"message-groups","enabled":true,"type":"remote-settings","bucket":"message-groups","updateCycleInMs":3600000}
browser.newtabpage.activity-stream.discoverystream.config {"api_key_pref":"extensions.pocket.oAuthConsumerKey","collapsible":true,"enabled":false,"show_spocs":false,"hardcoded_layout":true,"personalized":true,"layout_endpoint":"https://getpocket.cdn.mozilla.net/v3/newtab/layout?version=1&consumer_key=$apiKey&layout_variant=basic"} {"api_key_pref":"extensions.pocket.oAuthConsumerKey","collapsible":true,"enabled":true,"show_spocs":false,"hardcoded_layout":true,"personalized":true,"layout_endpoint":"https://getpocket.cdn.mozilla.net/v3/newtab/layout?version=1&consumer_key=$apiKey&layout_variant=basic"}
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.safebrowsing.provider.mozilla.lists base-track-digest256,mozstd-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,block-flash-digest256,except-flash-digest256,allow-flashallow-digest256,except-flashallow-digest256,block-flashsubdoc-digest256,except-flashsubdoc-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256,base-fingerprinting-track-digest256,content-fingerprinting-track-digest256,base-cryptomining-track-digest256,content-cryptomining-track-digest256,fanboyannoyance-ads-digest256,fanboysocial-ads-digest256,easylist-ads-digest256,easyprivacy-ads-digest256,adguard-ads-digest256,social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256 base-track-digest256,mozstd-trackwhite-digest256,google-trackwhite-digest256,content-track-digest256,mozplugin-block-digest256,mozplugin2-block-digest256,block-flash-digest256,except-flash-digest256,allow-flashallow-digest256,except-flashallow-digest256,block-flashsubdoc-digest256,except-flashsubdoc-digest256,ads-track-digest256,social-track-digest256,analytics-track-digest256,base-fingerprinting-track-digest256,content-fingerprinting-track-digest256,base-cryptomining-track-digest256,content-cryptomining-track-digest256,fanboyannoyance-ads-digest256,fanboysocial-ads-digest256,easylist-ads-digest256,easyprivacy-ads-digest256,adguard-ads-digest256,social-tracking-protection-digest256,social-tracking-protection-facebook-digest256,social-tracking-protection-linkedin-digest256,social-tracking-protection-twitter-digest256
browser.tabs.documentchannel false true
browser.tabs.remote.useHTTPResponseProcessSelection false undefined
browser.tabs.tabmanager.enabled undefined false
browser.xr.warning.infoURL undefined https://www.mozilla.org/%LOCALE%/firefox/xr/
devtools.debugger.features.async-live-stacks undefined false
devtools.recordreplay.cloudServer undefined
devtools.responsive.metaViewport.enabled false true
devtools.webconsole.input.eagerEvaluation undefined false
dom.audiochannel.audioCompeting false undefined
dom.audiochannel.audioCompeting.allAgents false undefined
dom.event.default_to_passive_wheel_listeners undefined false
dom.forms.requestsubmit.enabled undefined false
dom.ipc.plugins.allow_dxgi_surface undefined true
dom.manifest.enabled undefined false
dom.metaElement.setCookie.allowed false undefined
dom.security.featurePolicy.enabled false true
dom.security.featurePolicy.experimental.enabled undefined false
dom.serviceWorkers.idle_extended_timeout 300000 30000
dom.serviceWorkers.parent_intercept false true
dom.storage.next_gen false true
dom.targetBlankNoOpener.enabled false true
dom.vr.always_support_ar undefined false
dom.vr.always_support_vr undefined false
extensions.abuseReport.openDialog false true
extensions.blocklist.useXML true false
extensions.getAddons.compatOverides.url https://services.addons.mozilla.org/api/v3/addons/compat-override/?guid=%IDS%&lang=%LOCALE% undefined
extensions.htmlaboutaddons.discover.enabled true undefined
extensions.htmlaboutaddons.enabled true undefined
extensions.legacy.exceptions testpilot@cliqz.com,@testpilot-containers,jid1-NeEaf3sAHdKHPA@jetpack,@activity-streams,pulse@mozilla.com,@testpilot-addon,@min-vid,tabcentertest1@mozilla.com,snoozetabs@mozilla.com,speaktome@mozilla.com,hoverpad@mozilla.com undefined
extensions.webcompat-reporter.enabled false true
findbar.matchdiacritics undefined 0
fission.rebuild_frameloaders_on_remoteness_change false true
full-screen-api.unprefix.enabled 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.webrender.compositor.surface-pool-size undefined 25
gfx.webrender.enable-low-priority-pool undefined false
intl.charset.detector.ng.enabled undefined true
intl.charset.detector.ng.in.enabled undefined false
intl.charset.detector.ng.jp.enabled undefined false
intl.charset.detector.ng.lk.enabled undefined false
javascript.options.parser_defer_allocation undefined false
layout.css.column-span.enabled true undefined
layout.css.constructable-stylesheets.enabled undefined false
layout.css.moz-document.url-prefix-hack.enabled true false
layout.css.moz-touch-enabled.enabled true false
layout.css.text-underline-position.enabled undefined false
layout.css.xul-box-display-values.survive-blockification.enabled true undefined
layout.dynamic-reflow-roots.enabled false true
mathml.mfenced_element.disabled false true
media.audiograph.single_thread.enabled false true
media.mediacontrol.testingevents.enabled undefined false
media.peerconnection.mute_on_bye_or_timeout undefined false
media.peerconnection.sdp.strict_success undefined false
network.http.network_access_on_socket_process.enabled undefined false
network.trr.resolvers [{ "name": "Cloudflare", "url": "https://mozilla.cloudflare-dns.com/dns-query" }] [{ "name": "Cloudflare", "url": "https://mozilla.cloudflare-dns.com/dns-query" },{ "name": "NextDNS", "url": "https://trr.dns.nextdns.io/" }]
network.trr.send_user-agent_headers undefined false
network.url.useDefaultURI undefined false
permissions.default.xr undefined 0
permissions.delegation.enable false undefined
permissions.delegation.enabled undefined true
permissions.eventTelemetry.enabled false undefined
permissions.isolateBy.privateBrowsing false true
privacy.annotate_channels.strict_list.enabled false true
remote.enabled false undefined
remote.force-local true undefined
security.allow_parent_unrestricted_js_loads undefined false
security.block_Worker_with_wrong_mime false true
security.disallow_non_local_systemprincipal_in_tests undefined false
security.pki.crlite_mode undefined 1
security.remote_settings.intermediates.enabled false true
security.tls.version.min 1 3
services.sync.engine.bookmarks.validation.enabled undefined true
services.sync.engine.passwords.validation.enabled undefined true
signon.storeSignons true undefined
signon.userInputRequiredToCapture.enabled undefined true
svg.text-spacing.enabled false true
telemetry.number_of_site_origin.min_interval undefined 300000
toolkit.telemetry.enabled false true
urlclassifier.features.fingerprinting.annotate.whitelistTables mozstd-trackwhite-digest256 mozstd-trackwhite-digest256,google-trackwhite-digest256
urlclassifier.features.fingerprinting.whitelistTables mozstd-trackwhite-digest256 mozstd-trackwhite-digest256,google-trackwhite-digest256
urlclassifier.features.socialtracking.annotate.whitelistTables mozstd-trackwhite-digest256 mozstd-trackwhite-digest256,google-trackwhite-digest256
urlclassifier.features.socialtracking.whitelistTables mozstd-trackwhite-digest256 mozstd-trackwhite-digest256,google-trackwhite-digest256
urlclassifier.trackingAnnotationWhitelistTable moztest-trackwhite-simple,mozstd-trackwhite-digest256 moztest-trackwhite-simple,mozstd-trackwhite-digest256,google-trackwhite-digest256
urlclassifier.trackingWhitelistTable moztest-trackwhite-simple,mozstd-trackwhite-digest256 moztest-trackwhite-simple,mozstd-trackwhite-digest256,google-trackwhite-digest256
widget.content.gtk-high-contrast.enabled undefined true