Personally I like a forward riding position, that is, a position where my shoulders are forward the perpendicular line of my hips.
The reason is because I once took a '66 Honda 450 with a straight seat (no bumper at the back side) for a test ride.
I figured it didn't have much power, or as much as my Honda 750, so I kicked it out of a stop sign, well,
it jumped right out from under my and there I was, hanging on by my hands while my pervis was laying off the back of the seat. My hand was stuck on the throttle and awayyy we went, woohoo!
Luckily I was turning left, and as I leaned I kicked the ground hard enough with my left foot to give me
the boost I needed to get at least one gonad on the seat.
This, of course, allowed me to apply the brake/clutch etc., but not without causeing a sewvere heart-pounding in the process.
I took the bike (still have it) that was in 1995, but ever since then, I liked having my shoulders forward of my hips, just in case I get launched again, so as I'm ready to resist before I (potentially) get thrown off.
This is one reason I don't like the cruiser-style arrangement, the other is I can't fully straighten my legs at a light,
and therefore can't use the greatest amount of power in my legs for support while stopped.