I went through this exact process when I bought new seats. I ALMOST pulled the trigger on the Smitty's because someone said they felt the same as the Master's when you sit in them. (NOT THE CASE, Glad I didn't)
I decided to see for myself, so I went to the local 4WP to inspect, sit in all of them and play with the mechanisms.
The Smitty's had about 1/2" of play in the backrest when locked. The MC's had very little.
The Smitty's felt much stiffer than the MC's to me. They didn't feel like a suspension seat at all, but they were not too bad. I found the MC's to be much more comfortable.
The stitching underneath and the suspension system seems higher quality on the MC's.
The frame and the mounting tabs on the MC's appear to have nicer welds.
The XRC's did seem like pretty nice seats overall, but not on the same playing field as the MC's. Even though they look nearly identical, they are far from it.
I chose the MC's because I was able to afford them. BUT, I would probably consider the XRC's again if I were on a budget. They are pretty nice for the money.