While there may be a grain of truth to what your buddy says, I think he's yanking your chain.
Personally, I have enough HP already and the cost of those extra ponies wouldn't be worth it to me.
Others seem to enjoy wringing every last bit of power out of the drivetrain and think it's worthwhile to spend quite a bit of money for a few extra HP.
Ie, it all depends on what you want and how much you're willing to pay for it.