SL88 Studio: TP/100LR
SL88 Grand: TP/40WOOD
I'm finally in possession of both the SL88 Grand and the Roland A88 MkII to test run. After playing with both for awhile, I will almost definitely be returning the A88 MkII. I'm actually pretty torn, but I think in the end, it's pretty clear that the SL88 has the better action. However, the A88 has a better default velocity curve in my opinion, it felt a good amount better to play on in how the notes end up sounding and feeling in my performance. I spent awhile trying to match the velocity curve making my own custom one on the SL88, and I think I got it pretty close.
That's just my initial two cents, going to try to make a full review and comparison of the two as well. Regarding "heavy" action, I think it's kind of interesting, because you could argue the A88 has a lighter action than the SL88, sort of, but the A88 is also mushier, and it doesn't end up giving the feeling of a real piano the same way the SL88 does. Then again, the A88 might actually be closer to an upright... It's really hard to say, and I don't think there is a way to describe all the nuance of the two actions without playing it yourself.
Either way though, I think they're both really great actions at the end of the day, and you'd do great with either one.