I'll disagree just a bit on "heavier is better" and "used for a good deal". My FIL who is REALLY frugal (cheap) just bought a light-duty 5ft bushhog RD5 for his Cub Cadet 7260 with 27 PTO HP. He has a few suitcase weights in front. The tractor will lift something like 1200# at 24in, but this little cutter is only about 520#. The light weight is fine for his cutting needs and will reduce the tendency for the cutter to push him around in use. Much easier to HANDLE. $1250 with full guards and a shearpin. Typical stout Bushhog construction.
We looked at a number of used cutters. There were ones that looked nice, and appeared to have little use, and thus lower risk of needing major repairs. They were all only about 20-30% less than new. And there were a bunch of beat-to-he11 rust queens that would likely take 3 hours of repair work for every 1 hour of use. Maybe not, but one just cannot be sure.
With new, he has a known good-quality tool that will work correctly, last him a long time and NOT be just a bunch of maintenance and repair headaches. And he's quite proud of it!
- Jay