I run both the 1512 2.5d and the 1515 2.5d in my rc8. I really like both. Wheelies aren't a problem. It runs cool. The 1515 is a hunk of a motor for a buggy though, but it works fine. You will need to adjust punch control a tad to tame the torque but it will run bit cooler than the 1512 in my experience.
I would say to go with the 1512. I run a medusa 60mm v2 1500 that I run on 6s in a hyper8. Plenty of motor for that buggy, and the 1512 should be a bit more powerful than the medusa. A 1515 is more powerful than an xl feigao, so that sounds to be too much for a buggy.