Keep in mind that there are several versions of the "three card monte", which one are you refering to? The gimmicked one, or the "sleight of hand" one? Anyway, it all depends on your sorroundings doesn't it? The shell game requires a smooth pad or something, as you can't do it on a table. As the card monte, doesn't really require anything. If you do the ungimmicked monte, I would prefer that one, as the throwing of the cards is pure sleight of hand, and the cards can be examined at any time. Of course, the shell game can also be examined, but it does require the pad.
Having said this, which probably didn't help you too much

- I would say that the 3 shell game is a very funny game. it can really f**k with ppl mind and get a real laugh. You can make anything happen, and you can fool them at any time. If you want them to be correct, you can make them be correct, and opposite. That's not the case with the 3 card monte. So, in such a way, they are very different. So it depends on your specs as well. Are you fooling kids and want them to be correct, or do you want to sc*ew drunk people and mak'em have wrong all the time?
