The best is the one that works every single time you go to use it. There are lots of good ones. I've got a Rhino 172 and it is very well built and I've been very happy with it. Is it the "best"? Beats me, probably not because there are some that will cut much larger brush and cost a lot more. For a good quality medium duty 72" cutter with a slip clutch, I'd expect to pay between $1,500 and $2,000.
Rhino, Bush Hog, Woods, Land Pride, Brown and others all make good rotary cutters. Most of them have various grades or levels of mowers. As you might suspect, the lighter ones with a lower rated gear box that are cheaper, and the heavier ones with a thicker gauge steel on the deck and sides and a larger rated gearbox that will cut heavier/thicker brush are more expensive.
I would definitely get a slip clutch for cutting any brush. (You mentioned "reclaiming" land.) Learn how to set the spring tension on the friction plates. It's a 15 minute job once or twice a year.