Depends on what you need to cut - habitually. If you just need to make 1 pass to cut a bunch of heavy stuff (2-4" saplings, thick brush, etc.) and from then on plan to reasonably frequently re-cut the area (i.e., before things grow up too much), you might be best served with renting, or hiring someone with, a heavy duty cutter and large tractor. Once the heavy stuff is cut, you can thereafter get by with a wider, but lighter duty, brush cutter.
So, if you're going to be in the thick stuff habitually - a medium or heavy duty cutter seems prudent, and for a 3010, esp. if HST, you're somewhere in the 4-5 foot range, depending on manufacturer. I've a 5' Woods BB600 "medium duty" behind a 3410 GST, and at 1039 pounds I barely have enough tractor to handle the real thick stuff (brush cutter is just fine, it's a pto issue - sometimes need to make 1/2 swaths, i.e., straddle the cutter between a cleared area and the uncut stuff). I also have to use front weights or keep my FEL on in order to balance the tractor and have enough weight on the front wheels to make FWD useful. That said, Woods stuff tends to be heavier built than most.
If you're mainly going to be cutting long weeds, modest brush and similar stuff most of the time, get a "light duty" brush cutter - they're much much lighter (Woods BB60 - the light duty equivalent of my BB600 - weighs less than 600 pounds), cut grass better (at least it looks better), and 3pt strain and pto power are less of an issue for your 3010. In addition, that extra foot of cutting width (the 72" Woods light duty unit weighs many hundreds of pounds less than the 60" medium duty unit) sure makes the job go faster.
