I have owned two 90-Twos - I sold the last one recently because I just couldn't get into the grip. There are NO aftermarket grips for the 90-Two, unless you put a slip on rubber grip that people put on polymer handguns.
The 92A1 has all the improvements internally as the 90-Two, but it thankfully uses the normal style beretta grips. So, all the grip options available to the 92FS will work on the 92A1.
The front and back straps on the 90-Two are slippery to me. I tried several solutions to do something to the grip, but nothing worked well.
The 92A1 is my fav of all the railed incarnations of the 92 platform. It is a great gun, and I would recommend that over the 90-Two.
That being said, the 90-Two will be more of a limited gun, in that they will start importing them into the USA in more limited batches... It may also get discontinued, as the gun never really caught on.
If ya REALLY want a 90-Two, better get one now if ya have access to one... The 92A1 came out last summer and will be around a while. However - if ya justw ant the best of the two, I'd suggest the 92A1...
Mine:
90-Two
92A1