After putting some more miles on the Sargent I have to agree it's a little too hard and cupped for my tastes. I got a good deal on a used Corbin so I took the opportunity to compare the three seats before I returned the Sargent.
Stock, hard as a plank and about as comfortable as one. Should work well on track though:
Standard issue Japanese crotch rocket seat
Sargent, surprisingly hard foam with a specific "cupped" shape. It gets uncomfortable pretty quick IMO. You can only move around so much on this seat - you can hang off to some extent:
Very clean underside, looks professional.
Corbin, also a very hard foam but works better w/ my butt. I like the shape of this one the best for street duty. You can't hang off as easy as the others though:
Not quite as clean as the Sargent but not as "shop class project" as I was expecting
I think both the Sargent and Corbin seats are well made and showcase excellent craftsmanship. In the end though I'll be returning the Sargent and keeping the Corbin. I'll break out the stock seat for track duty when it comes around again.
I wasn't able to weigh any of the seats with a reliable gauge but the Corbin is easily the heaviest of the bunch. The Sargent is only slightly heavier than the stock which is the lightest.