I agree with Dswartz and will give you my opinion of the seats I have tried.
I had no issue with the stock seat but my better half wanted something more comfortable so we opted to try the HD Sundowner Deep Bucket Seat. This seat turned out to be very comfortable for the both of us.
Sundowner Classic Models | Harley-Davidson USA
Second seat was the Signature Series Seat with Rider Backrest. The ONLY thing I liked about this seat was the backrest. Neither myself or my better half thought this seat was as comfortable as the Sundowner Seat so thats what we went back to using.
Signature Series Seat with Rider Backrest - FLSTC Styling with Studs | Harley-Davidson USA
Aside form that, if sweating is an issue for you I would highly recommend getting a set of Beadriders. These are a big an improvement for me in keeping dry as well as being very comfortable on long rides.
BeadRider - Beaded Motorcycle Seats
This is what works for us