[G4 General] theslam08:
This is the wrong forum/place for this topic, but I'll throw my 2 cents out there as well. Everyone's phone is different, so I will try to simply point out software only differences. Also not to try and repeat what "marn3us" stated above. Pretty sure H815 or H811 don't matter, not with the comparison below.

For me, I really like the following

STOCK:

-In call floating pop up. Simply best feature I know, have not seen it on anything else really. While other end is ringing or talking, you can multi task and almost instantly get back to the call when they pick up or you're done doing other things. Sure w.out that floating bubble, one could pull down the notif panel but I personally find the bubble a bit more convenient (esp how you can move it around).

-VoLTE. I have LTE everywhere I live, so I like to take advantage of that. Also WifiCalling if I need it

-Lockscreen. I love how it works. If I have my phone in my pocket and somehow the screen gets turned on while I am trying to pull it out, if I accidentally tap a notification it does not automatically open. Stock lockscreen requires one tap of notif + full swipe then it will open that notif app. No way of accidentally opening apps showing notifications. Non-stock, double tap any notif and it opens...some ROMs are worse than others, with a broken prox sensor allowing you to open notifs even with screen off in your pocket...making all sorts of pocket activity (calls/text/etc.). The stock way of 'Click + Swipe below' for me works great. Also the prox sensor works 100% on stock ROMs so 100% of time in your pocket it will never have pocket action.

-Lockscreen Pt2: Double-tap to wake/sleep. Works almost every single time. I love the dt2s on LS (some ROMS do have this but with the bad way of simply double-tap a notif to open [on non-stock roms] sometimes I'll double tap the notification instead of turning my screen back off...errr.)

-Data/Service. I find stock has a much better response to reception. In some dead-zone places (like a basement), I have very low service. With non-stock, I almost always lose service completely in same area. Then it doesn't come back until I airplane toggle/leave dead-zone. Stock seems to give better reception everywhere.

-Incom Call Pop-up: Very nice with the ability to simply hide the pop-up and let the phone keep ringing. I found on non-stock there is no way to hide the pop up (actually maybe by a swipe now I think about it, though does that decline the call?).

For me, those 4-5 things are the main points why I cannot use anything other than Stock. Also for me, stock works perfectly fine. No lag and everything just works (I clear recents and restart every couple of days). I try new builds of non-stock all the time, a day or 2 then realize I am missing my fav features above so then I go back. I recently found out the LG SmartWorld app allows you to theme some parts of the UI (icons, fonts, some colors, etc.)..combined with the Tweaksbox, you can do some good Stock changes.

I never really had a problem with lag/performance. I also always used the Imperium kernel: http://xdaforums.com/g4/orig-development/kernel-imperium-kernel-g4-v1-0-t3282915 which seems to always do well for my phone. I also turn animations down to .5 in dev options, everytime I flash stock...makes it much quicker. I also know with stock, it's pretty much all optimized code for our phone...AOSP based miss a bunch of proprietary code which I think takes out some of the potential of this phone. Wish every company was like 1+, dev friendly.