Lets face reality, neither film maker were after cinematic praise when either of these films were made, but I can say the original is far better and worth the watch.
Piranha 3DD in my opinion is not worth the $4 to rent or the hour to download (for you illegal downloaders out there).
Granted there are a beavy of naked beauties in the film and some decent gore in parts but the terrible acting and ridiculously unbelievable plot out way any good.
The first half of the movie appears to be shot in a "normal movie" capacity then the second half of the flick turns into a "Scary Movie esk" type movie where the filmmaker is poking fun at the cast, himself, the movie and the audience.
I should make mention of the guest spot of David "The Hoff" Hasselhoff, who does the best job of poking fun at his stereotype. That did give a few chuckles.
So unless your an avid fan of movies such as the Scary Movie Franchise and other spoof comedies, give Piranha 3DD a miss.