I tend to agree with RAH on that six acres is not a place for a walk behind brush mower... that's a lot of walking lol.
I use both a Diesel tractor and a gas tractor to mow my property and I would take the Diesel over the gas any day. Much more power and can run for hours on a minimal fuel. The gas tractor certainly gets the job done but I am constantly refilling the tank.
For mowing with a tractor, find one without a front end loader as that can make mowing in tight places much harder. There are lots of other projects that I wish I had a front end loader but for mowing they can be difficult to maneuver.
