A dumbo is still a rat, so there really shouldn't be any difference, except for one thing. Right now the dumbo is the Rat du Jour, and people may be breeding them with a little extra care, whereas our topears could be from a feeder bin, a ratmill supplying a petstore, a badly bred oops litter, etc.
I have known of some very unpleasant dumbos, and some incredibly sweet standard eared rats...its all a lottery.