When I first bought my house with 2.5 acres, I had nothing to mow with. I got a good deal buying my 1070 from someone I know and it came with a woods 90" finish mower. It was way to big for my needs, but I figured it would get me by for now. My mother was looking for a mower for her 1 acre lot a couple years ago, so I talked her into a used JD 345 with 54" deck that was for sale about 30 mins from my house. The guy agreed to deliver to my house, and then I would take it to my mom's. While at my house, I decided I would mow with it once just to make sure all was well and it would give me an idea of what I was looking for to mow. Well last year I bought an old (about 1998) bunton 3 wheeled mower with 71" deck for cheap and needed to rebuild the engine. For those not familiar, these resemble a walk behind mower, but with a seat on the back with one wheel under your but, this wheel is steered with handlebars the will turn the wheel left or right. Maneuverability is near that of a 0-turn, but resembles a front deck mower, kind of a compromise between the two. My lot has a few things to mow around... a child swing set, trampoline, house, propane tank, 2 fire pits, and about 15 trees. I also keep about 200 feet of ditch mowed across the street from my yard.
So for mowing times...
-Deere 1070 (90") was about 1 1/2 hours but there was a lot left to mow, part of the ditches I couldn't mow, and I couldn't get as close to things.
-Deere 345 (54") was about 1 hour, 45 mins-maybe 2 hours, but didn't leave as much behind, I could mow all of the ditches.
-Bunton 3 wheeler (71") about 1 hour 15 mins, can mow ditches and can get very close to obstacles.
Now the tractor would also be harder on the lawn, it has turf tires, but the laminated wheels would leave bare spots around the trees where the wheels would track every time I mowed. The tractor is much more versatile though. The 345 was the most comfortable to mow with, takes up less space in the garage, and could have other uses (attachments). The bunton can only mow, can't even really pull a cart with it, but is much faster at mowing. It also goes through the most fuel (25 hp kohler command) and takes up a lot of floor space.
The reason I posted this is to show that deck size is not nearly as important as maneuverability, at least in most "lawn" type practices... in an open field is another story. The bunton is not in the nicest shape and will probably be replaced in the next few years. It will probably be replaced with something similar in size to the 345, maybe a x540 or something. It took a little longer to mow, but is much more useful and was much more pleasurable to mow with. It is also so easy to use, I could probably get the children to mow for me soon. The tractor and bunton are something that I think you need to be older to use.