U1 silent model seemed nice.
I was trying out U1 and U3 silent pianos when I was getting a new one, and something I noticed was that in silent mode, on U1 glissandos were much better, whereas on U3 I'm having difficulties depressing the keys enough to produce sound in glissandos. Overall, U1 seemed to respond a little easier.
Also, make sure the bass keys are sensitive enough in acoustic mode, because I've become highly frustrated at the banging sound of my U3's (I finally chose U3 because of the clearer sound) bass register, probably because of the silent mechanism their dynamics are practically uncontrollable and I'm considering a change for smaller or softer hammers.