I'll say beautiful and dumb with the clarification in thread that you wouldn't be completely mentally incapable of doing anything by yourself (as the original number of OP would suggest, I think). "really really dumb" is different than mental retardation.
being ugly is fine but I wouldn't want to be so overweight and never be able to control it, as per conditions of thread. Even assuming a more reasonable "totally overweight" number than the number in the OP, which would be like a morbidly obese person for their height or something that couldn't do anything, that would have a lot of challenges.
I would choose smart and ugly if the ugly was like overweight (but not so obese) and with some other problem, like say a burn mark on your face that left a romantically/aesthetically undesirable scar/skin but a normal face otherwise.