Re: Lay back seatpost - with or without support?
nobody's mentioned riding style yet. a bicycle seat and post (not to mention your butt, spine, pelvis, etc...) is not designed to take heavy shockloads.
look at the difference between motorcycle seats and the way they're mounted compared to a bicycle.
you should be "unweighting" yourself when hitting bumps.
that being said, i know there's always the unsuspected body jar out there, so if in doubt, go with the strongest possible.