It depends on the scale...
I have a 40 gallon FW, a 20 gallon 'pond', a newt tank, and a killie fry tank on the main level. We filter water into a trash can, downstairs. I bucket all my water, about 30 gallons a week.
For the 180 SW system, that is downstairs, we have a large tank on a cart. The water is mixed with salt in this one, heated, then rolled forward to the tank. There's a valve on the bottom, so the water just drains into the sump. Much easier than bucketing the water, since that would be 60 gallons every other week. When not it use, the cart stays in the fish room.
Okay, so it end up being 60 gallons every other week for either FW or SW, no matter how you look at it. I get screwed by having that stair case in the way. Maybe when I get the other tanks set up....