I currently have all three in my garage: BRP comfort seat, Corbin, and Ultimate Tall Boy. I have the Ultimate on right now. I'm going to do a write up with pictures on all three very soon. I want to do this because it is SO confusing on what to buy. Plus, I hate the standard answer of: "go to a motorcycle event and sit on them." Well, I am unable to do that.
I've ridden all three in the last couple of months with the idea of figuring out what is the best for me, and maybe someone else that is not sure either. Well, in summary, they each have their pros and cons, and there is nothing perfect.
In my opinion as of right now:
1. BRP Comfort seat. I think if you're riding here and there and nothing of long term, it is awesome. Its a soft seat. So it is comfy for short term, but not long. However, because it is soft, you can press into the little back wall of the driver's seat. I have long legs and it makes it easier to stretch them out. Corbin and Ultimate have hard boundaries. Now that I've ridden the Ultimate and Corbin seats, I've actually surprised that I like the BRP seat for other reasons. I figured that throwing money at something would make a huge difference. Again, it depends. Of all three seats, I feel like it gives me the most room for my legs.
2. Corbin. I loved the ability to customize the seat. I really liked the website and interaction. The seat has a PERFECT shape for a "butt." It reminds me of my very expensive custom saddle for my horse. It kind of has a tractor style shape. The craftsmanship is great. Big rivets hold the material down. The appearance is awesome. Love the look. It is very firm. Not hard, just firm. It rides lower and firmer. It really bothers me for two reasons: it is at a forward position, like a stock seat, and it is very slippery with vinyl. With my long legs, I felt very cramped with the position and more bend at the knees. It is the heaviest of the three, by a lot. It also does not use the seat prop from the stock seat, and it has weird hinges for the gas door. They look like they should go on your kitchen cabinets. Because of this, if you want to open the seat, you have to open the door. The hinges catch the side if you don't. I think if the seat was a bit back like the BRP Comfort seat, this would be a great seat for me. Someone told me that the "Lamonster" Corbin version is farther back. Well, I couldn't find that information on their site anywhere, and I don't particularly want the logo on my bike. I like his store and efforts around here very much!

But, just saying.....
3. Ultimate Tall Boy. I bought the black with black crock inlay. It looks a LOT better in person than on their website. I chose not to buy it first because it is not presented well on their website, in my opinion. The craftsmanship is excellent as well. The leather reminds me of a fine German car's upholstery. Its firmness is right between the Comfort seat and Corbin. It is the tallest of the seats. It may be as far back as the BRP Comfort seat, but it doesn't quite feel that way because of the rigid perimeter, but it is further than the Corbin. It's not nearly as heavy as the Corbin, but is more "solid" than the Comfort seat. The gas door is metal and hinged very well. It has a look like it should be a door for a gas tank. Tough. The seat uses the stock seat hardware, so it uses the seat prop. I haven't quite put on enough miles to give it a recommendation, but I'm pretty sure I'll be riding this one.
After all of this, I think the Corbin seat would have been perfect for me because I liked the lower position and firm ride. However, the forward and cramped feeling are deal breakers for me. I'm going to have to sell it. Someone will get a great deal on a lightly used custom Corbin seat. (Message me if you are interested.)
But the Ultimate doesn't completely win either. I think it would be a perfect seat for me if it was a little lower ride, and I could position myself back more like the BRP Comfort seat. But, I haven't had enough break-in period, and maybe it will change.
While the Ultimate seat is esthetically fantastic, and what I'll be riding, I probably would've kept riding my BRP Comfort seat if I knew the others wouldn't be perfect. Esthetically, it is kind of plain, and it is too soft, but I really like how I can stretch out on it. I would've added some firmness to it somehow.
I've taken a lot of pictures to show the differences of each and will put them together soon to show.