You don't speak the local language; are you looking to learn, to try to connect with the locals? An extended bus trip can provide that. If you're just trying to get from one place to another, personally, I'd take the plane.
Edit: did cross-county USA twice by bus: NYC to SF, and a few years later LA to Philly. It was an interesting experience. I'm glad I did those trips, and I'll by happy to not ever have to do them again.