If I had a big lawn, and had money, this is what I'd mow with:

A Bob-cat Zero turn radius mower
Best mower ever IMO... Cuts evenly, does a large section, and gives that professional look afterwards, 0 turn radius is nice to do a 180�° turn so the lawn doesnt look like someone was going in Foward, Reverse, foward, reverse, with the tire marks...
So far that thing is very reliable, started up fine in cold weather after sitting for a few months, (Probaly below 32�°F), However it had a sticker price of $7,000