Local dealers have residential mowers and you will get the support when needed. Check with a local Gravely/Ariens dealer.
Two acres
The type of engine, the type of hydro transaxles, and the overall build structure of the zero turn. Too many subtleties to go into. Going online and doing research is another good way to determine. In the $3500-$5500 big box store zero turn price range, you aren’t getting anything except a residential zero turn. It will do the job, however, it will have more problems than a beefier zero turn long term.
I purchased some big box stuff in ‘96 & ‘02 and they are still going nicely today maintaining 4acres. Recently, I purchased an XT254D which does have a heavier transaxle (tough-torq k62 from a dealer, dealer typically has upgraded options).But I was looking at the Craftsman 54” zero turn with Kohler from Lowe’s. The transaxles have the same pump/flow as my new Cub. I prefer the Kohler because the added HP does not tax/strain the smaller engines, which some manufacturers put into a line.
Craftsman is MTD and so is Cub Cadet. When viewed from a distance, the only noticeable difference is the color.
Typically the mower will fall apart before the engine. But hey, things happen.