50 gallons of bio-media? I never heard of that, please explain as I don't understand.
I should learn not to use numbers when making points... 5 gallons, 50 gallons, 500gallons. The point is that on a normally stocked tank, once you've got space for ENOUGH bio media (which usually isn't very much), adding more is useless.
Yeah, but again, that's not a wet/dry anymore, it's a refugium. you can use a refugium with a canister too, you just have to put it in a different place. I'll agree with your point here on some level, I use my one remaining sump as a fuge all the time... I'd still get rid of it in a blink if I had some money burning a hole in my pocket.1) can be used as a refugium
Dunno why this is a big thing... do you swap your media around a lot? I don't. Comes back I guess to what I said about if you like to mess with your filter set up a w/d is good. Although... personally I shut the pumps off whenever disturbing the media so all the crud doesn't get pumped into my tank.3) can change out filtration media w/o shutting down the system
Again, this is only an advantage if you want to mess with your filtration a lot. The way I run my tanks lately (since I lost interest in screwing around with my filters.) is to choose an option that works and then leave it alone. As long as there's one option available that will do a good job, what does it really matter how many different other options there are?4) more flexibility for both filtration media and bio media
Refugium, not a w/d. Can have plants in a refugium above the tank, beside the tank, or in the tank with a canister. Again I suppose it's easier with a sump, but we're not really talking about a straight wet/dry anymore.5) can have plants etc as a bonus item.
Those are the reasons I listed for myself in my decision to go wet/dry over canisters. Canisters would cost me over $600 and the wet/dry 1/2 that. It fit my long term plans better and more efficiently.
Cost is a big one, especially for a large tank. That's the reason I went wet dry sump in the beginning (and why one of my tanks still has a wet dry.) I wound up buying a canister anyway though, and I have two wet dry's I built for myself along with all their associated equipment sitting in my yard cultivating spiders.