This is difference between the default preference of Firefox 41.0 beta 1 and one of 41.0.

Default pref Javascript files (Firefox 41.0 for Linux x86_64):
(omni.ja){/greprefs.js,/defaults/pref/services-sync.js}, (browser/omni.ja)/defaults/preferences/{firefox.js,firefox-branding.js,firefox-l10n.js}, (webapprt/omni.ja)/defaults/preferences/prefs.js
Default pref Javascript files (Firefox 42.0 beta 1 for Linux x86_64):
(omni.ja){/greprefs.js,/defaults/pref/services-sync.js}, (browser/omni.ja)/defaults/preferences/{firefox.js,firefox-branding.js,firefox-l10n.js}, (webapprt/omni.ja)/defaults/preferences/prefs.js
PrefFirefox 41.0Firefox 42.0 beta 1
app.update.cert.checkAttributestruefalse
app.update.cert.maxErrors5undefined
app.update.cert.requireBuiltIntruefalse
app.update.certs.1.commonNameaus4.mozilla.orgundefined
app.update.certs.1.issuerNameCN=DigiCert Secure Server CA,O=DigiCert Inc,C=USundefined
app.update.certs.2.commonNameaus4.mozilla.orgundefined
app.update.certs.2.issuerNameCN=Thawte SSL CA,O="Thawte, Inc.",C=USundefined
app.update.urlhttps://aus4.mozilla.org/update/3/%PRODUCT%/%VERSION%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xmlhttps://aus5.mozilla.org/update/3/%PRODUCT%/%VERSION%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xml
apz.allow_zoomingundefinedfalse
apz.minimap.enabledundefinedfalse
browser.display.show_loading_image_placeholderundefinedfalse
browser.newtabpage.enhancedundefinedtrue
browser.preferences.inContenttrueundefined
browser.readinglist.enabledfalseundefined
browser.readinglist.sidebarEverOpenedfalseundefined
browser.tabs.showAudioPlayingIconundefinedtrue
browser.trackingprotection.gethashURLhttps://tracking.services.mozilla.com/gethash?client=SAFEBROWSING_ID&appver=%VERSION%&pver=2.2https://shavar.services.mozilla.com/gethash?client=SAFEBROWSING_ID&appver=%VERSION%&pver=2.2
browser.trackingprotection.updateURLhttps://tracking.services.mozilla.com/downloads?client=SAFEBROWSING_ID&appver=%VERSION%&pver=2.2https://shavar.services.mozilla.com/downloads?client=SAFEBROWSING_ID&appver=%VERSION%&pver=2.2
browser.urlbar.maxCharsForSearchSuggestionsundefined20
browser.urlbar.userMadeSearchSuggestionsChoiceundefinedfalse
captivedetect.canonicalContentundefinedsuccess
captivedetect.canonicalURLundefinedhttp://detectportal.firefox.com/success.txt
captivedetect.maxRetryCountundefined5
captivedetect.maxWaitingTimeundefined5000
captivedetect.pollingTimeundefined3000
datareporting.healthreport.service.providerCategorieshealthreport-js-provider-defaulthealthreport-js-provider-default,healthreport-js-provider-beta
devtools.debugger.promiseundefinedfalse
devtools.debugger.tracerfalseundefined
devtools.devedition.promo.enabledfalsetrue
dom.audiochannel.mutedByDefaultundefinedfalse
dom.broadcastChannel.enabledtrueundefined
dom.ipc.plugins.asyncInitundefinedtrue
dom.ipc.plugins.asyncInit.enabledfalseundefined
dom.mozPay.enabledtruefalse
dom.performance.enable_notify_performance_timingundefinedfalse
dom.permissions.enabledundefinedfalse
dom.popup_allowed_eventschange click dblclick mouseup reset submit touchendchange click dblclick mouseup notificationclick reset submit touchend
dom.presentation.discoverableundefinedfalse
dom.presentation.discovery.enabledundefinedtrue
dom.push.enabledfalsetrue
dom.push.maxQuotaPerSubscriptionundefined16
dom.requestcontext.enabledundefinedfalse
dom.serviceWorkers.enabledfalsetrue
dom.serviceWorkers.interception.enabledundefinedfalse
dom.serviceWorkers.interception.opaque.enabledundefinedfalse
dom.system_update.debugundefinedfalse
dom.system_update.enabledundefinedfalse
dom.vr.cardboard.enabledundefinedfalse
dom.vr.oculus.enabledundefinedtrue
dom.vr.oculus050.enabledundefinedtrue
full-screen-api.approval-requiredtrueundefined
full-screen-api.transition-duration.enterundefined200 200
full-screen-api.transition-duration.leaveundefined200 200
geo.wifi.xhr.timeoutundefined60000
gfx.vr.mirror-texturesundefinedfalse
identity.sync.tokenserver.uriundefinedhttps://token.services.mozilla.com/1.0/sync/1.5
image.decode-only-on-draw.enabledtrueundefined
image.infer-src-animation.threshold-msundefined2000
intl.ime.use_simple_context_on_password_fieldtruefalse
layers.async-video-oop.enabledtrueundefined
layers.async-video.enabledtrueundefined
layout.css.prefixes.gradientsundefinedtrue
layout.frames.force_resizabilityfalseundefined
loop.feedback.dateLastSeenSecundefined0
loop.feedback.formURLundefinedhttps://www.mozilla.org/firefox/hello/npssurvey/
loop.feedback.periodSecundefined15770000
loop.seenToSunseenundefined
loop.showPartnerLogotrueundefined
media.block-play-until-visibleundefinedfalse
media.format-reader.mp4trueundefined
media.format-reader.webmundefinedtrue
media.getusermedia.audiocapture.enabledundefinedfalse
media.gmp-manager.certs.1.commonNameaus4.mozilla.orgaus5.mozilla.org
media.gmp-manager.certs.1.issuerNameCN=DigiCert Secure Server CA,O=DigiCert Inc,C=USCN=DigiCert SHA2 Secure Server CA,O=DigiCert Inc,C=US
media.gmp-manager.certs.2.commonNameaus4.mozilla.orgaus5.mozilla.org
media.gmp-manager.certs.2.issuerNameCN=Thawte SSL CA,O="Thawte, Inc.",C=USCN=thawte SSL CA - G2,O="thawte, Inc.",C=US
media.gmp-manager.urlhttps://aus4.mozilla.org/update/3/GMP/%VERSION%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xmlhttps://aus5.mozilla.org/update/3/GMP/%VERSION%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xml
media.mediasource.format-readerfalsetrue
media.mediasource.format-reader.mp4trueundefined
media.mediasource.format-reader.webmundefinedfalse
media.mediasource.whitelisttrueundefined
media.peerconnection.ice.default_address_onlyundefinedfalse
media.peerconnection.ice.link_localundefinedfalse
media.peerconnection.ice.relay_onlyundefinedfalse
media.useAudioChannelAPIundefinedfalse
media.useAudioChannelServiceundefinedtrue
media.video-queue.send-to-compositor-sizeundefined9999
network.auth.allow-subresource-authundefined2
network.auth.subresource-http-auth-allow2undefined
network.captive-portal-service.backoffFactorundefined5.0
network.captive-portal-service.enabledundefinedfalse
network.captive-portal-service.maxIntervalundefined1500000
network.captive-portal-service.minIntervalundefined60000
network.generic-ntlm-auth.workstationundefinedWORKSTATION
network.http.enablePerElementReferrerundefinedfalse
network.jar.block-remote-filesundefinedfalse
network.predictor.max-uri-lengthundefined500
nglayout.debug.invalidationundefinedfalse
privacy.clearOnShutdown.passwordsfalseundefined
privacy.sanitize.migrateClearSavedPwdsOnExitundefinedfalse
privacy.trackingprotection.introCountundefined0
privacy.trackingprotection.introURLundefinedhttps://www.mozilla.org/%LOCALE%/firefox/%VERSION%/tracking-protection/start/
privacy.trackingprotection.pbmode.enabledfalsetrue
reader.errors.includeURLsundefinedtrue
readinglist.scheduler.enabledfalseundefined
readinglist.serverhttps://readinglist.services.mozilla.com/v1undefined
services.sync.prefs.sync.privacy.clearOnShutdown.passwordstrueundefined
services.sync.tokenServerURIhttps://token.services.mozilla.com/1.0/sync/1.5undefined
signon.recipes.pathundefinedchrome://passwordmgr/content/recipes.json
signon.rememberSignons.visibilityTogglefalsetrue
toolkit.telemetry.optoutSampletrueundefined
toolkit.telemetry.unifiedIsOptIntrueundefined
urlclassifier.disallow_completionstest-malware-simple,test-phish-simple,test-unwanted-simple,goog-downloadwhite-digest256,mozpub-track-digest256test-malware-simple,test-phish-simple,test-unwanted-simple,test-track-simple,test-trackwhite-simple,goog-downloadwhite-digest256,mozstd-track-digest256,mozstd-trackwhite-digest256
urlclassifier.trackingTablemozpub-track-digest256test-track-simple,mozstd-track-digest256
urlclassifier.trackingWhitelistTableundefinedtest-trackwhite-simple,mozstd-trackwhite-digest256