As I can remember Minimalistic Text
was the fastest of them all. Minimalistic, plain text...
I never really used it cuz numbers in Russian spells much longer then English to look pretty and appropriate
Later then I moved from UCCW to Zooper, as I can remember because Zooper worked just faster and smoother. I should check out modern version of UCCW
So if you want much more options then MT - I'd recommend Zooper for now
I'd like to add a bit to the original question — what's the difference in features of Zooper and UCCW we have, and how much does it cost for battery and speed?