Kerrits, Noble Outfitters, Irideōn, and Devon Aire are all very comfortable. Noble Outfitters breeches are on the pricier side but definitely worth every penny. I have their signature front zip and am absolutely in love with them :)
Horse pilot do the best breeches I've ever worn. The fabric is grippy but not too much and pre-formed. They are higher in the back so they dont slip down and very comfortable to wear and extensible. They exist in many colors, the only drawback is of course the price.
FITS are my favourite breeches of all time! They last forever and ate surprisingly warm in winter, yet cool in summer! They have a full seat but it's only on the parts where you touch the saddle so you don't have extra fabric near your crotch, it also has a tummy panel, and they're just so comfortable!!! Great grip towards the saddle... quite pricey but I can assure you 100% that you'll never go back! The ones that I'm talk about is the PreformMAX full seat and they are the best things ever!! Check them out!!
My all time favorites would be tailored sportsmans, but the price limits how many pairs i can get lol:p The smartpak piper breeches are super nice quality and for a reasonable price but the only drawback is that they are a thicker material and seem to make me really hot when i use them in the summer. Kerrits are probably my favorite summer breeches! While not always the trendiest, they are sooo breathable and the price is unbeatable!