What about the de10 esc for raceing 17.5 and 7.5

I don't think it would be bad but I also don't think that after factoring in the cost of it and the programmer, it would be any better than buying a used higher-end ESC to start with. For example, you can find something like a used LRP SXXv.2 in the for-sale ads here in that sort of price range and it'll be smoother no matter how much time you spend tweaking the Duratrax one.