I don't know about bicycle racing, I don't race, but nothing could be further from the truth in motorsports. The brakes are the most important equipment you have. If I can beat someone into the corner, I can hold them off in the straight. I would assume there is a similar strategy in bike racing.
It's nothing like in motor sports. Brakes are not a factor in races, excepting for steep descents and for stopping before you add to a pileup. Most of the time, if you touch your brakes, you'll lose positions in the pack.
Good brakes are more important in regular riding around, so you can stop for lights and stop signs. If you ride hills then they may be important on the descents.
If I were getting this bike, I'd try out the stock brakes and pads, and then replace the pads with Shimano pads if the braking isn't very good. Also check the setup- make sure the pads hit the brake tracks nice and square, and are toed-in to prevent squeal.