what Tx Reef said. It's easier. seems complex but it's not.In my experience having gotten a tank with a sump for the first time, everything is easier and more convenient. There is space for all the equipment under the tank. If I need to add or remove equipment, it is much simpler. If something needs replacing, I have more flexibility with what to replace it with.
I can't really think of a single thing that is made harder by having a sump...