Well, both have goodsides and badsides. If you are using an external overflow, it can lose suction and you dry run your pump. Canisters on the other hand don't skim the surface and rid the tds floating on the surface. W/D may build up nitrates, but you can make it a w/d/refugium and have plants to export those nutrients. Canisters can clog up with waste making it harder for BB to do their job. Overflows can be a bit noisey, canisters are basically pretty quiet. Both are very efficient. But with a W/D you have more control over the amount of water movement. With 2 1" drain pipes you can get about 1300 gph of water flow, Use something that holds about 75 gallons for a W/D and put a pump that moves about 1200 gph and you will be good to go. Only fill the sump about 1/4 total heighth, and have your drains about even with the frame and you should be good to go either way. Canisters are no brainers, and only put out their max gph when new.
I have both, the W/D is far less maintenance, but the canister is far less a pain in the *** since it doesn't lose suction.