Put it this way:
Two women (or men), one not too attractive (17") but a good ride the other a stunner (18") but a reasonable ride.
Which one would you go for?
I know one thing, the doggy one would not give me a hard-on even though she/he was supposed to be a good ride. So it would be a waste.
On that note, I'll have the stunner and have satisfaction guaranteed.
Different strokes for different folks and all that jazz .....