from my short lived experience, i started with no sump, got a sump, loved it. now due to a relocation and lack of space for a sump, I really miss having one.
The think I like most about it is the level in the display tank stays the same, and just fluctuates in the sump. A sump also makes it easier to add equiptment like skimmers and calc reactors.
If you're thinking about having a sump, dooooo itttttt! Just don't cheap out on the overflow, or drill if you can
