If you ride regularly with a passenger then the Corbin passenger seat with backrest is a worthwhile investment. I ride a lot with my wife and she appreciates the Corbin. You do need to "break in" the seat though, it's pretty firm when new, but conforms to your shape over time and gets more comfortable with use.
So far I haven't felt the need to replace the stock seat up front however, so I can't comment on Corbin/Tobin/Gel differences.