Baffles and compartments give your sump that neat and tidy look and they help to channel the flow of water. But a lot of people just have one open space in their sumps. Water in from display tank at one end into a filter sock for mechanical. Big pile of rocks, rings, whatever, in the middle for bio. And pump at the other end. You're still getting the flow of water through your sump.Why would you not use baffles or compartments?
My current sumps are just the standard 3 compartment type. But any future sumps I run I will probably go with the more basic open plan design. It's purely up to each individual.