There are so many good buggies out there it's hard to choose from. I'd first check you local hobby shops which ones they carry spares for. After that, I'd look at a few things. How long the buggy has been out, reliability, parts included in the kits, costs of spares, cost of kit. I wouldn't buy a older kit, mostly cause it may be discontinued quicker than something that is more recently released.
The Jammin X2 buggy
Losi 2.0
Hot Bodies D8
Kyosho MP9
These are the ones I'd look at for me. I recently picked up the D8 due to potential performance, cost of the kits and spares, and ease of maintenance. These were important factors to me, so I even picked up two kits at the same time to provide enough spares for a long time.
Really, now days it's easy to get a good buggy/truggy without blowing the bank or choosing between one or two companies.