ORIGINAL: Derigor
which ever is easier for you to get spare parts for.
It was easier for me to get HPI parts locally (they tend to have a good US distributor to my LHS's) while Tamiya parts I'd have to get through evilBay or from online stores.
Both are very good affordable beginner cars.
I think he said it best! There is nothing worst then waiting for parts to ship...
I would do this...take the pro's and con's for each and come to a conclusion base on the info you gather and decide base upon your results. Either way you can't go wrong. Both HPI and Tamiya make good quality RC's. I was in the same boat as you a while ago and ended up not even getting what I origanally wanted. I ended up getting a Sprint 2 Flux...