Does size really matter

If you think you will ride fast at all at certain times, then you need to get something with resi shocks.  Yeah, the bigger buggies will ride better.  They are also getting close to the size and price of a new Jeep.  

As for a used unit, I would have to say a used Rhino, Teryx, or 900xp would be your best bet.

I understand about good set of shocks with reservoir on them I have a set on my 4 wheeler. They can make the difference between a long rough day or a really good day for sure . I've been reading up on Polaris A Arm and trailing arm set-ups and Can Am TTA system . I see the trailing arm set-up is on the XP's do they get hung up on rock and trail obstacle a lot ?

I haven't had any issues with the arms on my 900xp gettin caught up on anything..

Some buy the curved arms for the xp for more clearance.  The ones in the very back that go from the rear knuckles to the frame in the center behind the diff.  They are curved up in the middle to about the same height as the axles and are made out of bigger tubing.  I don't think it's a big problem though.  I wouldn't worry about it if I had one.