Yeah, well i thought the "U" was due to the the platform was mounted on tracks instead of wheels.. but all the Russian designations can be a challange.. at least for me.
The Radar on Pantsir-S2/S2U is a new design with a paired ESA array from its older versions. It get a better real time picture this way.
And the new Pantsir is a modular system, it can link up with S-400 command unit for better SA.
https://www.youtube.com/watch?v=HQwOD6IoY58
I'm not sure if Tor-M2U can link up with S-400 system, it being an Army unit and all.. perhaps it can link up with the upcoming S-350 system once it get operational.
Speaking of S-350, it is a beefed up BUK system, right?
https://www.youtube.com/watch?v=sS2d5QRkKZk
Looks like a twelve tube launcher, and the idea of reloading it is probably much faster and easier than the standard BUK systems.
Edit:
Never mind, S-350 is not the same missile as BUK. The size is clearly different, seen here:
https://www.youtube.com/watch?v=Y2czmbM7Vro
So S-350 fields a smaller new missile.. interesting.