[Sprint LG Optimus G] I-IoLLoW:
If they did a hard reset it is possible that it wiped everything but not a definite. I purchased my phone from Best Buy and was on zvb. When the zvc update came through it messed my phone up(which is why you don't take OTA's once rooted without further knowledge/modifications) so I took it to Best Buy and they said they did a hard reset to fix it. It worked, my phone booted back up and my internal was fine. However, that's Best Buy and they barely know what they are doing so it may have been a soft reset, I am not 100% sure. As for a new root for the update, I received another phone shortly after because the glass back on mine broke and Best Buy replaced it with a whole new phone. It was on zvc and I used an app named Framaroot with the Gandalf exploit option and it worked fine for me. I have heard of others having issues with that method but for me, it worked and has stuck.

Fiddy619's universal root method seems to be the preferred way for our phone, look in the general section here for a thread by engine95 to see what I mean. After I rooted with Framaroot I then used FreeGee and unlocked the bootloader then made a total nandroid backup of my stock in TWRP before going further. I also copied the backup to my PC just in case.

As for my preferred roms, if we are talking about Android 4.4 both Vanir and PSX are my personal favorites. However as you can tell from my signature I am still using stock zvc android 4.1.2. I have flashed just about every rom available for our phone but my daily driver is stock that I have modified manually(different kernel, removed bloat ware, minor modifications and tweaks, etc). For android 4.3 I have had the best experience with CM10.2 and cfxe. I have not tried CM11(based on 4.4) for awhile but it seems to have overwhelming support - Cyanogenmod usually does.

Really when it comes to roms it's personal preference. They are all very similar with different tweaks/additions. As for which one is the most stable that is also a tricky question. Even though we have the same model of phone, I have seen how picky they can be from one to the other. My roommates have the EXACT same phone, installing CM10.2 worked fine for two of us, but one lost GPS and I had to fix it.

My best advice for when you get your new phone is to backup your working stock and then have fun flashing different things making sure you follow the instructions per rom exactly. It's always a good idea after making your backup(if planning to install another rom) to wipe everything except your internal storage and do a clean install of the rom and gapps. Then, test it for a day or so because sometimes it takes time to settle in. It's a shame that Optimus DE gave you issues, it was rock solid for me, again, these phones are picky! But one of the main reasons I stayed with stock is because the AOSP based cameras leave much to be desired when compared to the LG camera. Again it's just personal preference because some don't like the lg camera.

If you have any other issues or questions I will be glad to help if I can. A lot of the people you see who are active on the forums are very knowledgeable, as long as you ask politely most will be glad to help. :)