I use either, or both, or.... whatever. Sometimes I use a bipod, sometimes I use shooting sticks (made from fiberglass tent poles of a tent that was too far worse for wear), sometimes I use monopods.
My most common "technique" is a 9-13" Harris bipod mounted on the rifle, which suits for prone if I need it, and keeps my rifle or shotgun out of the wet grass or snow the rest of the time. Even with that mounted, I'll use a Primos Trigger stick monopod for my seated shooting.
The Trigger Stick Monopod gets most of my work. My wife uses the same technique but with a Trigger Stik Bipod.