I think the original is more creepy. I watch it all of the time. There's like 0 comedy in the OG. The few lighthearted moments that they have, are instantly turned somber. There was never a sense that the kids got to enjoy life, and they carried into adulthood. These kids have their moments of fun. The town/residents of Derry are also given more life, even through the kids just interacting with them. The mini also moves at a slower pace, with mostly dialog which adds to the mood of Derry, while this is clearly made to be a movie.
I disagree with those that say Tim Curry was overacting. He acted as a clown, a clown with some effed up tendencies. This Pennywise acted as a creature tryna mimic a clown. IMO, that's the difference in the 2 performances.