The original. But do go in realizing that, compared to the reputation is now has, it's deliberately paced. The Cebonites largely don't even enter the movie until over half-way through, and are relatively minimal. The real monsters in the original film are the humans. Think of Beetlejuice... he's the only character you remember, but he's only in the film for about 17 minutes. It's sort of the same here.
In fact, trivia... Pinhead is only credited in the original film as "Lead Cenobite". The name hadn't even kicked in yet.