My favourite is Xiaomi.eu Custom ROM (they are not affiliated with Xiaomi). It's the latest version of MIUI straight from China. I don't like MIUI, but it has Xiaomi's Vibration tweaks, MIUI Dolby, and the MIUI Camera App.
On AOSP ROMs you only get a basic Open Source Camera that can only utilise 12 MP,
Vibration is awful on AOSP, because Xiaomi has made some tweaks in MIUI for it to feel good, even tho the Vibration-motor is very cheap.
Non-existant Dolby Atmos or bad versions of Dolby Atmos, which makes the Loudspeakers sound rather unimpressive.
I dislike MIUI because it's such an heavily modified version of Android, and the UI isn't pleasing me and it has some problems like No Gesture support on 3rd party launchers, however it's the features that I need.
If you care about the camera and audio, and want the best experience overall, Xiaomi.eu is the way to go. In fact, MIUI based roms not only have that, but also a blazing fast charge.
However, I don't care much about camera or listening to audio using the phone speakers, and the battery lasts for the entire day, so I can leave it charging with an average charger, so my daily driver is Pixel Experience. Not only the UI (imo) is better than MIUI, but the phone has better performance during games and daily work, and it will be improving in each release.