plunk..if it's your first 1/8 buggy, you're gonna crap your pants no matter what engine you get, even if it's an OS .21RG.

the Mugen Ninja will make it haul ass around a track (And seems easy to tune...unfortunately i don't own one), the V-spec is what I'd go for if it weren't for the things I've read about it on this forum (which may or may not be user error, but given the skill level of most of these guys, I'd say it's not), but i'd recommend one of the SH based .21s available (the Sportwerks engine is solid, quick, and reliable as a claw hammer)