Default [Q] Best ROM for everyday life? (Xperia U)

A friend owning a Xperia U is not satisfied with his phone, especially since he updated it to latest official version.
I proposed him to try a CM (or any sibbling ROM) because it's what I know and have on my phone (Motorola Defy).
I browse the dev forum and there is many options and versions available so I want to know wich is best for everyday life, I mean:
- stability is important
- battery life is important
- phone and wifi must be rock solid
- UI must be responsive
- but really don't care about video playback, camera, fm, music or playing games

Thanks for your advices and feedback.