Wow, that's a tough choice, actually. I have Jurassic Park and I love it. In fact, I played it for about 2 hours straight last night. There are quite a few modes, the T-Rex is awesome (just keep it clean), and the theme is very well done. Both games play well, but I think the novelty of Jurassic Park probably holds up a bit longer.
Honestly, I think you're going to get some split decisions on this one, with people leaning toward which ever machine they are more familiar with. I think Jurassic Park is the best game Data East put out, and it holds up well, but I also remember Dracula being good fun too.
I do remember Dracula being a little frustrating with how many missed shots lead to drained balls, however. That probably has as much to do with my skills than the machine though.