This is difference between the default preference of Firefox 54.0 beta 3 and one of 53.0.

Preference difference
PrefFirefox 53.0Firefox 54.0 beta 3
apz.allow_with_webrenderundefinedfalse
browser.crashReports.unsubmittedCheck.enabledfalsetrue
browser.formautofill.enabledundefinedfalse
browser.formautofill.loglevelundefinedWarn
browser.migrate.automigrate.enabledfalsetrue
browser.newtabpage.activity-stream.enabledundefinedfalse
browser.newtabpage.remotefalseundefined
browser.newtabpage.remote.content-signing-testfalseundefined
browser.newtabpage.remote.keysundefined
browser.newtabpage.remote.modeproductionundefined
browser.newtabpage.remote.version1undefined
browser.safebrowsing.provider.google.reportMalwareMistakeURLundefinedhttps://%LOCALE%.malware-error.mozilla.com/?hl=%LOCALE%&url=
browser.safebrowsing.provider.google.reportPhishMistakeURLundefinedhttps://%LOCALE%.phish-error.mozilla.com/?hl=%LOCALE%&url=
browser.safebrowsing.provider.google4.listsgoog-phish-proto,googpub-phish-proto,goog-malware-proto,goog-unwanted-protogoog-badbinurl-proto,goog-downloadwhite-proto,goog-phish-proto,googpub-phish-proto,goog-malware-proto,goog-unwanted-proto
browser.safebrowsing.provider.google4.reportMalwareMistakeURLundefinedhttps://%LOCALE%.malware-error.mozilla.com/?hl=%LOCALE%&url=
browser.safebrowsing.provider.google4.reportPhishMistakeURLundefinedhttps://%LOCALE%.phish-error.mozilla.com/?hl=%LOCALE%&url=
browser.safebrowsing.reportMalwareMistakeURLhttps://%LOCALE%.malware-error.mozilla.com/?hl=%LOCALE%&url=undefined
browser.safebrowsing.reportPhishMistakeURLhttps://%LOCALE%.phish-error.mozilla.com/?hl=%LOCALE%&url=undefined
browser.storageManager.pressureNotification.minIntervalMSundefined1200000
browser.storageManager.pressureNotification.usageThresholdGBundefined5
browser.urlbar.usepreloadedtopurls.enabledundefinedfalse
browser.urlbar.usepreloadedtopurls.expire_daysundefined14
devtools.devedition.promo.enabledfalsetrue
devtools.gridinspector.showGridOutlineundefinedfalse
devtools.source-map.locations.enabledundefinedfalse
devtools.sourcemap.locations.enabledfalseundefined
devtools.toolbox.toolbarSpec["splitconsole", "paintflashing toggle","scratchpad","resize toggle","screenshot --fullpage --file", "rulers", "measure"]undefined
dom.archivereader.enabledfalseundefined
dom.event.highrestimestamp.enabledfalsetrue
dom.forms.select.customstylingundefinedfalse
dom.ipc.plugins.asyncdrawing.enabledfalsetrue
dom.ipc.plugins.forcedirect.enabledundefinedtrue
dom.ipc.processCount.extensionundefined1
dom.moduleScripts.enabledundefinedfalse
dom.timeout.max_consecutive_callbacksundefined5
dom.vr.puppet.enabledundefinedfalse
dom.vr.test.enabledundefinedfalse
extensions.blocklist.detailsURLhttps://www.mozilla.com/%LOCALE%/blocklist/https://blocked.cdn.mozilla.net/
extensions.blocklist.itemURLhttps://blocklist.addons.mozilla.org/%LOCALE%/%APP%/blocked/%blockID%https://blocked.cdn.mozilla.net/%blockID%.html
extensions.blocklist.urlhttps://blocklist.addons.mozilla.org/blocklist/3/%APP_ID%/%APP_VERSION%/%PRODUCT%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/%PING_COUNT%/%TOTAL_PING_COUNT%/%DAYS_SINCE_LAST_PING%/https://blocklists.settings.services.mozilla.com/v1/blocklist/3/%APP_ID%/%APP_VERSION%/%PRODUCT%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/%PING_COUNT%/%TOTAL_PING_COUNT%/%DAYS_SINCE_LAST_PING%/
extensions.e10sMultiBlocksEnablingundefinedtrue
extensions.screenshots.system-disabledundefinedtrue
geo.security.allowinsecureundefinedtrue
gfx.downloadable_fonts.keep_variation_tablesundefinedfalse
gfx.downloadable_fonts.otl_validationundefinedfalse
gfx.webrender.enabledundefinedtrue
image.mem.animated.discardableundefinedfalse
image.mem.sharedundefinedfalse
intl.uidirectionundefined-1
intl.uidirection.arrtlundefined
intl.uidirection.fartlundefined
intl.uidirection.hertlundefined
intl.uidirection.ugrtlundefined
intl.uidirection.urrtlundefined
javascript.options.shared_memoryfalsetrue
layers.advanced.border-layersundefinedfalse
layers.advanced.caret-layersundefinedfalse
layout.css.appearance.enabledundefinedtrue
layout.css.clip-path-shapes.enabledfalsetrue
layout.css.moz-appearance.enabledundefinedtrue
layout.css.object-fit-and-position.enabledtrueundefined
layout.css.text-justify.enabledundefinedfalse
layout.css.unprefixing-service.enabledtrueundefined
layout.scrollbars.always-layerize-trackundefinedfalse
marionette.enabledundefinedfalse
marionette.forcelocalundefinedtrue
marionette.log.levelundefinedinfo
marionette.portundefined2828
marionette.prefs.recommendedundefinedtrue
media.eme.apiVisibletrueundefined
media.eme.vp9-in-mp4.enabledundefinedfalse
media.ffmpeg.low-latency.enabledundefinedfalse
media.peerconnection.ice.tcpfalsetrue
network.http.pipeliningfalseundefined
network.http.pipelining.abtestfalseundefined
network.http.pipelining.aggressivefalseundefined
network.http.pipelining.max-optimistic-requests4undefined
network.http.pipelining.maxrequests32undefined
network.http.pipelining.maxsize300000undefined
network.http.pipelining.read-timeout30000undefined
network.http.pipelining.reschedule-on-timeouttrueundefined
network.http.pipelining.reschedule-timeout1500undefined
network.http.pipelining.sslfalseundefined
network.http.proxy.pipeliningfalseundefined
network.http.referer.hideOnionSourceundefinedfalse
network.throttle.enableundefinedtrue
network.throttle.resume-forundefined2000
network.throttle.suspend-forundefined2000
pointer-lock-api.prefixed.enabledfalseundefined
privacy.firstparty.isolate.restrict_opener_accessundefinedtrue
security.data_uri.inherit_security_contextundefinedtrue
security.mixed_content.hsts_priming_cache_timeout10080604800
security.sandbox.content.levelundefined2
security.sandbox.content.syscall_whitelistundefined
security.sandbox.content.write_path_whitelistundefined
security.sandbox.logging.enabledundefinedtrue
security.tls.version.max34
services.sync.engine.bookmarks.validation.intervalundefined86400
services.sync.engine.bookmarks.validation.maxRecordsundefined1000
services.sync.engine.bookmarks.validation.percentageChanceundefined10
services.sync.jpake.firstMsgMaxTries300undefined
services.sync.jpake.lastMsgMaxTries300undefined
services.sync.jpake.maxTries10undefined
services.sync.jpake.pollInterval1000undefined
services.sync.jpake.serverURLhttps://setup.services.mozilla.com/undefined
services.sync.log.logger.service.jpakeclientDebugundefined
services.sync.log.logger.userapiDebugundefined
services.sync.miscURLmisc/undefined
services.sync.privacyURLhttps://services.mozilla.com/privacy-policy/undefined
services.sync.scheduler.sync11.singleDeviceInterval86400undefined
services.sync.serverURLhttps://auth.services.mozilla.com/undefined
services.sync.statusURLhttps://services.mozilla.com/status/undefined
services.sync.syncKeyHelpURLhttps://services.mozilla.com/help/synckeyundefined
services.sync.termsURLhttps://services.mozilla.com/tos/undefined
services.sync.userURLuser/undefined
services.sync.validation.interval86400undefined
services.sync.validation.maxRecords100undefined
services.sync.validation.percentageChance10undefined
toolkit.identity.debugfalseundefined
toolkit.identity.enabledfalseundefined
Default pref Javascript files
PrefFirefox 53.0Firefox 54.0 beta 3
browser/omni.ja.d/defaults/preferences/debugger.jsN/Apresent
browser/omni.ja.d/defaults/preferences/devtools.jspresentpresent
browser/omni.ja.d/defaults/preferences/firefox-branding.jspresentpresent
browser/omni.ja.d/defaults/preferences/firefox-l10n.jspresentpresent
browser/omni.ja.d/defaults/preferences/firefox.jspresentpresent
browser/omni.ja.d/defaults/preferences/webide-prefs.jspresentpresent
omni.ja.d/defaults/pref/marionette.jsN/Apresent
omni.ja.d/defaults/pref/services-sync.jspresentpresent
omni.ja.d/greprefs.jspresentpresent