dak is spot on about the exaggeration factor - usually about 25-30%, between the golf drive distance and the tennis serve speed. (except coach Lee is probably on the high end of the spectrum with 50% exaggeration).
this is no different from male animals open up their feathers to look bigger, to the female or the enemy.
on the other hand, distance/speed is not even the most important factor.... I'd take 85mph hitting both corners or curving into the body, over 100mph but right into the receivers strike zone.... and I'd take 225 drive down the middle over the 275 in the trees.