I am an Orvis fan for heavy outerwear (waders, wader boots, heavy rain jacket, etc.).
When it comes to warm weather gear, I go with Patagonia almost exclusively. I have a pair of the Merrell wet wading shoes( http://www.amazon.com/Merrell-Mens-W...7331888&sr=1-1
) that are really good. This is of course for when I am in a boat or the water is warm enough that I don't mind dipping my toes in for several hours at a time.
I have never tried Simms gear, but then I am still on my first pair of waders. Gear can get expensive, but to me it is worth it. If I get Wal-Mart waders they may last half a season. If I buy some (insert Simms, Orvis, etc.) gear then it is expected to last a while.
I would consider myself very loyal to Orvis and Patagonia, and I only see that changing if either company were to really start pumping out garbage gear.