Parts availability is a major concern with racing. You should go with something that has lots of upgrade parts avail so you can build what you are going to need to win as you go along. I don't Have a lot of experience with hpi but the other posts seem to have answered that question. If it between those 2 alone, the traxxas seems to be the only choice.Def let us know what you choose, or if you choose a different kit based on local parts availability. You Def should be checking out what the other ppl who are racing are running. Talk with the ppl at the track. They will be able to answer a lot of the questions as well.