The XRay is already a dated Chassis( set up for 4 cells)- At least here in Florida. Especially if your going to be running a single cell lipo .Out of your two choices I'd go Associated. Otherwise look at the Darkside Chassis. I don't drive any of these chassis.
Team Epic/Trinity -Michael Bruce Hobbies-Team CRC ,Kimbrough Products GForce and RJSpeed.
WGT-R, GT Racing USA (17.5 foam),RJSpeed- Legends &Spec Mod, MudBoss and 386 RaceWay.