Ive used both, I have a drum. Would say if its in the budget go widebelt. the belt will not fetch up as easily as the drum and not wear a trench in your stock. Also, with the platen you can control the pressure of the paper on the stock. Also, a widebelt is going to be a bit more accurate.
Another is the ease of changing paper. its easier to open a door release the tension slide out one belt slide on another reset tension and go. With the drum you have to cut your paper to length and wrap/unwrap it each grit. doesn't sound like a lot but when you do it a few times you start to see the benefits.
Anyway, hope that helps