Timber is right on. How big is big? I mow about 3 acres with a rider Cub Cadet 48" cut. But I have 3 tractors that never are used for lawn. For pure lawn work, you will be hard pressed to find anything better than a Zero Turn. By the time you get so big that a tractor is better than a Zero Turn, you are looking at a dern large tractor pulling a gang mower like they use at the golf course.
Now, if you want to expand your weekend fun with other implements and a front end loader, then you can't beat a tractor. Kubota BX, B, L, Grand-L. I think you can get a 40+ hp grand L with a mid-mount mower. If you are talking "BIG" you can look into the M tractors. A turbo charged 105 hp tractor pulling a 30 ft wide gang mower will keep hundreds of acres looking nice. Much like the lawn size question, how "big" is your budget?
jb