A basic Hasselblad is fairly light. Add a couple more lenses to the camera bag, and an extra back, and a prism finder, and suddenly it's not so light. My 4x5 field kit weighs less than my Hasselblad kit.

If your concern is image quality, there's no argument. Either one will make excellent pictures. Size and weight seem to be the major issues. Yes, you might have to crop a Hasselblad frame to fit your image to a particular paper format, but so what? 120 film is so fine-grained now, you shouldn't see grain in an 11x14" enlargement. I happen to like the square format. Some people don't.

Finally, there's price. RBs seem to go for less. They're big and kind of clunky, but they're excellent cameras. Take your pick.