As far as my favorite, it's a toss-up between my Irideon Powerstretch winter breeches and the Kerrits performance tights. Equestrian Collections carries the Powerstretch breeches in up to 3X, and they are sooooo darn comfy. I wear them around the house all the time--the fleece is so snuggly soft, it's like getting a warm hug all day long.
The Kerrits are great for the summer, they are very durable and forgiving if your weight fluctuates or your proportions are weird. I was able to weight the 1X (tho Equestrian Collections has them up to 2X) when my hips were measuring 54". Now I'm down to a slightly less bootilicious 47" butt, and they still fit well.
I've been much less happy with Tuffrider plus-sized breeches.