Sump is good, next best thing to a canister filter. In fact it is as a variety of chamber based filter is widely used, I use it twice, both on my 260 gal tank.
As shake mentioned, it keeps your surface free of any trash or oily film and your water level stays constant.
It is such a great place to dump all of your equipment and keep them from view of the main tank. Thermometer, heater, chiller, CO2 reactor, fert autodoser, automatic water changer.... the list keeps adding up.
Sure there is extra CO2 ougassing when you compare it to canister setup, but who cares? The outgassing is still of acceptable level that you need no extreme measure just to even it up. Not to mention CO2 is plentiful and dirt cheap to refill, so point of whining because your gas tank empties a bit earlier because you crank extra 1 bps to compensate.
Just make sure you do not combine your sump with trickle filter/wet n dry system...