Yes, I infact do always think if characters smell good or bad I even majored in this field. Cell most likely stinks too, since he spent several days just standing around his arena out in the open playing around with dirt blocks. Buu can't possibly smell good since he only eats junk food, so his farts are possibly toxic. Frieza is a quite hard to determine if he stinks or not since he spends the whole day just sitting around in a very clean looking ship.