i have raced plenty of stock yfz's when my xx was stock, and beat them, and it goes about the same as i mod i could beat faster ones.
the major advantage of the yfz is that it gets off the line alot quicker.
BUT i also have a 06 yfz450 with fully built race motor and suspension. and the two down even compare. the yfz beats it everytime. everywhere. drag,trail,mx. even on a top end roll down a long road the yfz won. the only thing that sucks is when trail riding the yfz dont have reverse.