The HD comfort stitch seat is similar to the seat that comes on the Electra Glide Classic and Ultra. Having owned an Ultra I can tell you it's not a bad seat, but if you do multi day riding it's too soft. IMO, it looks kind of big and bulky on a SEEG. But remember there are two basic truths about motorcycling... you can either look cool or be comfortable. It's rare that you can have something that is both at the same time

Corbin on the other hand, well cheek, is much more firm and great for long distance riding once the seat is broken in (takes about 2000 miles to break in a Corbin). I have two Corbin seats for my SEEG, a "dual tour" and also a "stinger". If I were to pick just one it would be the "dual tour" as it is wider and also allows for two up riding. Add the rider backrest and it's a great package. The downsides to Corbin are the cost and their customer service is almost non-existent. Since the seat is firm you'll feel more of the bike and road vibrations through the seat. And depending on your size, the seat may move you back too far. The best way to buy a Corbin is at a rally or at their Daytona or California locations where you can try different seats on the bike and then have them make adjustments when they build your seat.
I've also had a Mustang seat on a Road King and it was a happy medium between the soft HD seats and the firm Corbin seats. They do tend to sit higher and move you more forward.
Another option to consider is Saddlemen. They custom build seats based on your physical characteristics (weight, height, etc) and have options like gel pads, heaters, etc. I have never ridden on one of their seats. My friend John, who has an orange / black SEEG, has one on order. He has always been a Corbin fan, but was not happy with the dual tour seat he purchased for a cross-country trip.
Some seats are good for 100 miles, some for 300 and some for hundreds more per day. All butts are different so what works for one person doesn't work for another. And bottom line (no pun intended) is that there is no "perfect" seat and any seat that you ride on long enough will become uncomfortable.