This is difference between the default preference of Firefox 25.0 beta 3 and one of 24.0.

Default pref Javascript files (Firefox 24.0 for Linux):
(omni.ja){/greprefs.js,/defaults/pref/services-sync.js}, (browser/omni.ja)defaults/preferences/{firefox.js,firefox-branding.js,firefox-l10n.js}
Default pref Javascript files (Firefox 25.0 beta 3 for Linux):
(omni.ja){/greprefs.js,/defaults/pref/services-sync.js}, (browser/omni.ja)defaults/preferences/{firefox.js,firefox-branding.js,firefox-l10n.js}
PrefFirefox 24.0Firefox 25.0 beta 0
app.update.checkInstallTimeundefinedtrue
app.update.checkInstallTime.daysundefined63
browser.download.animateNotificationsundefinedtrue
browser.download.useJSTransferundefinedfalse
browser.sessionstore.debugundefinedfalse
browser.sessionstore.upgradeBackup.latestBuildIDundefined
datareporting.healthreport.service.providerCategorieshealthreport-js-provider-defaulthealthreport-js-provider-default,healthreport-js-provider-beta
devtools.browserconsole.filter.netwarnundefinedtrue
devtools.debugger.enable-content-actorsundefinedfalse
devtools.inspector.remoteundefinedfalse
devtools.profiler.ui.show-platform-dataundefinedfalse
devtools.webconsole.filter.netwarnundefinedtrue
dom.future.enabledfalseundefined
dom.navigator-property.disable.mozSettingstrueundefined
dom.promise.enabledundefinedfalse
dom.use_watchdogundefinedtrue
dom.webapps.useCurrentProfileundefinedfalse
extensions.hotfix.certs.1.sha1FingerprintCA:C4:7D:BF:63:4D:24:E9:DC:93:07:2F:E3:C8:EA:6D:C3:94:6E:8991:53:98:0C:C1:86:DF:47:8F:35:22:9E:11:C9:A7:31:04:49:A1:AA
general.useragent.complexOverride.moodlefalseundefined
javascript.options.pccounts.chromefalseundefined
javascript.options.pccounts.contentfalseundefined
layers.bufferrotation.enabledundefinedtrue
layers.frame-counterundefinedfalse
layers.prefer-memory-over-shmemundefinedtrue
layers.use-deprecated-texturesundefinedtrue
layout.css.filters.enabledundefinedfalse
layout.css.osx-font-smoothing.enabledundefinedfalse
media.mediasource.enabledundefinedfalse
media.peerconnection.turn.disabletruefalse
media.video_stats.enabledundefinedtrue
media.webaudio.enabledfalsetrue
network.disable.ipc.securityfalsetrue
network.tickle-wifi.delayundefined16
network.tickle-wifi.durationundefined400
network.tickle-wifi.enabledundefinedfalse
nglayout.debug.paint_flashing_chromeundefinedfalse
plugins.click_to_playfalsetrue
ril.numRadioInterfacesundefined1
security.ssl.enable_false_startfalsetrue
security.ssl.enable_ocsp_staplingundefinedtrue
security.ssl.false_start.require-forward-secrecyundefinedfalse
security.ssl.false_start.require-npnundefinedtrue
services.sync.scheduler.eolIntervalundefined604800
svg.marker-improvements.enabledundefinedfalse
svg.text.css-frames.enabledfalsetrue
toolkit.telemetry.serverhttps://data.mozilla.comhttps://incoming.telemetry.mozilla.org
xpinstall.whitelist.add.36getpersonas.comundefined