I have winter breeches, and the rest of the year breeches. The winter ones are knee patch only, but they are a polar fleece. I do not need any thermal underwear under them. They are pullon, no zipper. Relatively cheap, last forever.
The other breeches are full seat pull on, but I have had better quality zip fronts before. I prefer the cotton, myself, but they will wear out faster than an artificial fabric, such as the ribbed ones mentioned earlier. (I , too , hated that feel of these, the Irideons)
I liked my On Course Cotton Naturals, full seat. They have a nice thick feel. Can be hot in the summer.
Now I rdie in Boinks. They are thin, though, so I used silk leggings under them in the fall or early Spring.
Breeches will stretch, so if in doubt, buy on the smaller side. Full seat will take a while and it can be so tight at first that you feel like you wont' be able to get you leg over the saddle and sit down in it well, but they stretch quite a lot.
The tightness helps to support you thigh muscles and feels really good , once you get used to it. No wrinkles under your thigh.
Kerrits makes some nice breeches. I think my winter breeches are made by them.
Clarino for the full seat is a good faux leather product. Leather is awesome, but pricey.