I started with Losi a few years ago and Ive had a few other cars along the way... to me Losi just has the best over all package: the car, part support etc. I went that way because that's what some of the local guys ran. Always liked watching Drakes how to vids when he was with Losi too.
All of them are good: Mugen, tekno, Losi.. Kyosho is another big one in 1:8 I would look at too. Best thing would be to talk to guys at your local track.