I just recenlty sold my RC18T because I never had time to run it. I really liked it. Compared to the Mini-T, I think it's a better truck. RC18T/B/MT are all the same. Only very small cosmetic defferences. Nothing in regards to meat and potatoes like suspension, steering, drive train, etc. Tires are the biggest factor between them.
As for the X-Ray, I've seen it and it looks really cool. I'm not sure about it's handling. The suspension seems better, though. I haven't seen anybody actually run one. The one I saw was a shelf queen.
The mini-LST seems to handle very well for a mini Monster truck. It has a lot of body lean. A guy at my local track ran one and it worked really well on a medium sized dirt track. It handled well on jumps and rough bumps in the track.
Good luck on your serach.