What's The Best Option For Me?

I'm new to Android and am going to get my first Android phone soon and I wanted to know what you guys would be best for me. I'm stuck on an AT&T family plan so signing a new contract is totally fine. I would love to have the Nexus 4 for stock Android, but it lacks LTE. Also, HSPA+ speeds aren't that great in the SF Bay Area. My other option is to get an Android phone on AT&T and root it.

My question is, how easy/hard is it to root and rom? Is it stable enough to use as a daily driver without problems, including LTE and all camera apps? Does the autoupdater work just like OTA updates from Google on the Nexus? And how fast do these custom roms get updates when new versions of the OS comes out?

Lastly, what device would you pick if you had a time frame until the end of December? The Nexus or any phone on AT&T's network? Let me know which one you would pick and why.