Interesting how everyone votes for whatever they have. I wonder how many people have actually tried more than one or two other truggies.
Anyways... I'm currently running a mugen MBX-6T Mspec and a Losi 8ight-T 2.0 Roller. I also have an RC-8T, BCE Cen Matrix TR, and formerly own a kyosho ST-RR.
that said, if you're looking for something that's stout and isnt going to keep breaking on you, go with the losi or the mugen. True, the mugen front a-arms' weak point are where the droop screws attach, but that's about it. Personally, I'm faster with the mugen, but I still need to do some tweaking on the losi. Running either the mugen m-spec or the losi 8ight T, you should re-shim the rear diffs. Also, on the mugen- change out the diff seals with the ones that tony's screws sells. Your diffs will last much longer.
Bottom line, however... make sure your LHS has parts for whatever you get.