Not really true, unless you are doing something like drag racing or top speed contests, racing is 90% skill and 10% setup, and most of that setup is finding the right tires and traction chemicals, and then making the right adjustments. If it is a really tight track and club level racing, the good racers out there could be winning with brushless and NIMH, on most tracks you could still build a brushed system that wouldn''t max out except on the longest straight, the only thing you have is the 13.5 or 17.5 motor in the stock class.

A good rubber cleaner and rubber traction goop is going to be around $10. to $15., slicks matched to the surface (as soft as you can use, 28''s or 32''s typically) are $39. or so; both these things are so much more important than a brushless. A brushless is a nice thing after that, for the no maintainance required thing, but you can win without it.

Take the time to set up your car right, and practice pleanty on the track; those things are much more important in general racing.

And off-road it matters even less, but again the no-maintainance is a big help esp. if you have never raced before since you'll want to spend a lot of time running for practice.