I've had a RolleiTLR, a Mamiya TLR and a Pentax 645. Head shots are difficult with the Rollei due to minimum focus distance and paralax. The C330 eliminates the focus distance problem and has some compensation for parallax. It also gets unwieldy to use handheld when shooting portraits with the lens racked way out. Still, it would be a reasonable choice since the square is a nice format for portraits. In the end though, I'd recommend an SLR. The Pentax is a great camera if you can live without interchangable backs and low flash sync. It is much like a big, easy to hold 35mm. I also have the whole thing (camera, 3 lenses) in a very small bag.
Throwing another option out there......If close focus work is not an issue and you shoot a normal lens mostly, I'd definitely consider a Rollei simply because it is a joy to use (I sold the Mamiya, but not the Rollei). It is small and light and you can easily take it anywhere. It also breaks the ice nicely with people you might be photographing.