Definitely go and try some on. I bought a pair of Ariat full seat and they are fine around the waist but the butt is soooo baggy. The full seat is so uncomfortable. I still wear them cause I paid a fair bit for them but I don;t think they are very flattering. I have a pair of Ariat with just the knee patches and they fit wonderfully, so comfy and fit my butt.
I have some cheapo breeches too that I bought on special at various sales that I love, some Dublin and Windsor ones. They fit well and are nice breathable fabrics.