UCX II here. I wouldn’t bother with the older ones, they’re quite dated and the difference in price isn’t worth it.
It’s been solid overall. Can’t really say much extremely positive or extremely negative about it. I’m not overly keen on total mix although it does everything I need.
UCXII ticked all the boxes for me for what I needed I/O wise, as well as for using with the ARC remote. There are some annoying limitations too (like you can only use one ARC remote at a time, and the TotalMix FX are so ugly and “Reaper-like” that I just bought hardware compressors to avoid using them.