This is difference between the default preference of Firefox 45.0 beta 5 and one of 44.0.2.

Preference difference
PrefFirefox 44.0.2Firefox 45.0 beta 5
accessibility.loadedInLastSessionundefinedfalse
apz.asyncscroll.throttle100undefined
apz.asyncscroll.timeout300undefined
apz.cross_slide.enabledfalseundefined
apz.fling_snap_friction0.015undefined
apz.overscroll.spring_stiffness0.0010.0018
apz.overscroll.stretch_factor0.50.35
apz.touch_move_toleranceundefined0.03
apz.touch_start_tolerance0.22222220.1
apz.x_skate_highmem_adjustundefined0.0
apz.y_skate_highmem_adjustundefined0.0
browser.cache.max_shutdown_io_lagundefined2
browser.esedbreader.loglevelundefinedError
browser.safebrowsing.allowOverrideundefinedtrue
browser.safebrowsing.forbiddenURIs.enabledundefinedfalse
browser.sessionstore.debug.no_auto_updatesundefinedfalse
browser.sessionstore.privacy_level_deferred1undefined
caret.manages-android-actionbarfalseundefined
datareporting.healthreport.service.providerCategorieshealthreport-js-provider-defaulthealthreport-js-provider-default,healthreport-js-provider-beta
devtools.appmanager.enabledtrueundefined
devtools.appmanager.lastTabhelpundefined
devtools.appmanager.manifestEditor.enabledtrueundefined
devtools.devedition.promo.enabledfalsetrue
devtools.markup.collapseAttributeLengthundefined120
dom.compartment_per_addonfalsetrue
dom.ipc.plugins.asyncdrawing.enabledundefinedfalse
dom.push.debugfalseundefined
dom.push.loglevelundefinedoff
dom.w3c_touch_events.enabled02
extensions.interposition.enabledundefinedtrue
extensions.interposition.prefetchingundefinedtrue
extensions.webExtensionsMinPlatformVersionundefined42.0a1
identity.fxaccounts.remote.force_auth.urihttps://accounts.firefox.com/force_auth?service=sync&context=fx_desktop_v1https://accounts.firefox.com/force_auth?service=sync&context=fx_desktop_v2
identity.fxaccounts.remote.signin.urihttps://accounts.firefox.com/signin?service=sync&context=fx_desktop_v1https://accounts.firefox.com/signin?service=sync&context=fx_desktop_v2
identity.fxaccounts.remote.signup.urihttps://accounts.firefox.com/signup?service=sync&context=fx_desktop_v1https://accounts.firefox.com/signup?service=sync&context=fx_desktop_v2
identity.mobilepromo.androidundefinedhttps://www.mozilla.org/firefox/android/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=
identity.mobilepromo.iosundefinedhttps://www.mozilla.org/firefox/ios/?utm_source=firefox-browser&utm_medium=firefox-browser&utm_campaign=
image.onload.decode.limit0undefined
layers.offmainthreadcomposition.force-basicfalseundefined
layout.accessiblecaret.extendedvisibilityundefinedfalse
layout.accessiblecaret.hapticfeedbackundefinedfalse
layout.css.float-logical-values.enabledundefinedfalse
layout.css.grid-template-subgrid-value.enabledundefinedfalse
layout.css.ruby.enabledtrueundefined
layout.css.text-emphasis.enabledundefinedfalse
loop.contextInConversations.enabledtrueundefined
loop.facebook.shareUrlundefinedhttps://www.facebook.com/sharer/sharer.php?u=%ROOM_URL%
loop.feedback.baseUrlhttps://input.mozilla.org/api/v1/feedbackundefined
loop.feedback.productLoopundefined
loop.gettingStarted.latestFTUVersionundefined1
loop.gettingStarted.seenfalseundefined
loop.oauth.google.redirect_uriurn:ietf:wg:oauth:2.0:oob:autoundefined
loop.oauth.google.scopehttps://www.google.com/m8/feedsundefined
loop.ringtonechrome://browser/content/loop/shared/sounds/ringtone.oggundefined
loop.support_urlhttps://support.mozilla.org/kb/group-conversations-firefox-hello-webrtchttps://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/cobrowsing
media.getusermedia.aec_delay_agnosticundefinedtrue
media.getusermedia.aec_extended_filterundefinedtrue
media.mediasource.webm.audio.enabledfalsetrue
network.dns.blockDotOnionundefinedtrue
network.dns.localDomainsundefined
network.jar.block-remote-filesfalsetrue
network.offline-mirrors-connectivitytruefalse
security.pki.cert_short_lifetime_in_daysundefined10
security.ssl.enable_ocsp_must_stapleundefinedtrue
selectioncaret.detects.longtaptrueundefined
selectioncaret.observes.compositionsfalseundefined
selectioncaret.visibility.affectscaretfalseundefined
services.sync.prefs.sync.network.cookie.lifetime.daysundefinedtrue
services.sync.prefs.sync.network.cookie.thirdparty.sessionOnlyundefinedtrue
services.sync.syncedTabsUIRefreshundefinedfalse
touchcaret.extendedvisibilityfalseundefined
urlclassifier.disallow_completionstest-malware-simple,test-phish-simple,test-unwanted-simple,test-track-simple,test-trackwhite-simple,goog-downloadwhite-digest256,mozstd-track-digest256,mozstd-trackwhite-digest256,mozfull-track-digest256test-malware-simple,test-phish-simple,test-unwanted-simple,test-track-simple,test-trackwhite-simple,test-forbid-simple,goog-downloadwhite-digest256,mozstd-track-digest256,mozstd-trackwhite-digest256,mozfull-track-digest256
urlclassifier.forbiddenTableundefinedtest-forbid-simple
webgl.disable-DOM-blit-uploadsundefinedfalse
webgl.webgl2-compat-modeundefinedfalse
Default pref Javascript files
FileFirefox 44.0.4Firefox 45.0 beta 5
browser/omni.ja!/defaults/preferences/devtools.jspresentpresent
browser/omni.ja!/defaults/preferences/firefox-branding.jspresentpresent
browser/omni.ja!/defaults/preferences/firefox-l10n.jspresentpresent
browser/omni.ja!/defaults/preferences/firefox.jspresentpresent
browser/omni.ja!/defaults/preferences/webide-prefs.jspresentpresent
omni.ja!/defaults/pref/services-sync.jspresentpresent
omni.ja!/greprefs.jspresentpresent
webapprt/omni.ja!/defaults/preferences/prefs.jspresentpresent
browser/features/loop@mozilla.org.xpi!/chrome/content/preferences/prefs.jsN/Apresent

Note: Firefox Hello (a.k.a. Loop) has been moved to a system add-on since Firefox 45. (ref Bug 1223573)