Everybody's butt is different, but I had the Corbin Dual Platform seat that lowers the rider about 2 inches and I didn't like it at all. It always seemed to be sliding me into the tank to the point where I had to brace my feet against the pegs when slowing down and stopping. I kept it for a few thousand km's and then sold it and bought a Seat Concepts kit (standard height). The Seat Concepts seat is much more comfortable and I know they make a lowered seat as well. I have no experience with their lowered model, but it might be worth checking out for you.
I have the Corbin dual, and my experience is exactly the same as 650stew's - always feel like I'm sliding forward.
Fast, good, cheap - choose two.
The Bluejay: 2009, EM 685 kit, Corbin seat, Wow LED tail light, rear DirtRacks bars, Shorai, Cee Bailey windshield, Superbrace, UNI air filter, EM Doo, KLX needle, T-Bob, de-snorkeled and box drilled, JNS bigfoot, skid plate, and aux light bar, SW Motech crash bars, Cycra hand guards, LeoVince X3, T-mod, Ernie Bell clutch arm, Cogent Pro Shock rear and DDC front, Galfer SS brake lines front/rear, MC Mod, Rox Anti-vibe Risers, Idabiker H7, many more...