I've been looking into getting a race worthy 1/10 TC as well for the past month or so. There are several cars that seem to always be at the top of the pack. It would really depend on parts support, which car you should probably pick up.
Personally, I'm leaning towards the TOP Photon, because it seems to be one of the best designed and performing kits (reasonably priced too) and there is a place near me that sells the kits and parts. Plus I dig the red anodizing
Next choice for me would be HB Cyclone TC, Schumacher Mi4LP or Tamiya 416 as I could get parts for any of those pretty easily. I think the Tamiya is a bit too expensive compared to some of the others. I'd say the same about the Kyosho Stallion. No one sells Kyosho near me anyway.
The X-Ray T3 is one of the most popular kits in the USA, but no shop near me sells them or can even order parts, so it rules that one out for me.
There are a few other kits I would look at if any hobby shop even remotely close to me sold them or could order parts. Yokomo BD5, Corally RDX Phi 09 and Zakura Zero.
I was considering the Team Associated TC5 at first, because it is one of the least expensive kits here and most of the shops near me sell it, but I've just read a few too many things that lead me to believe it might be a bit more difficult to dial in compared to some of the others. I saw a kid win a pretty big comp with one recently, but I don't think he was running very much of the stock kit. I know for sure he was using an exotek chassis.
Anyway, this is just my newb opinion after some limited research, but I'm probably going to go for a TOP Photon.