Okay, i own both and i have upgraded and raced and bashed the hell out of both.

Stock, The rustler WILL rape the gt in a straight line, BUT stock on the track the GT will rape the rustler, spend 50 bucks on both and the rustler is faster on track and in drag and spend a lot and the gt is the best.

Ill attempt to explain.
The Rustler has a very powerful engine package, so standard it will beat a gt in a drag. But the gt is a nicer set up car so on the track it wins. To get the rustler up to racing ability, spend 50 bucks and do some things, modify shock mounting positions, change springs and oil, add downtravel limiters and set it up and it will beat a GT on the track due to its engine, even if the gt has got the same 50 bucks spent on it, but the gt has most of these things done okay stock and the rusty wins again because of the engine, but a FACTORY TEAM GT, will beat a rustler anyday, and it is because of weight and geometry, with a fair bit of money into both neither would have stock engines, so the rustlers advantage is gone and the GT is quicker by a couple seconds a lap.

Dann