BTS (blade tip speed) is where it's at along with what type of mower (mulching/discharge), type of blades, grass height. Some mowers are geared better than others.
I think the MMM on my Kubota doesn't have a fast enough BTS, especially being it's a side discharge (or can be converted to a mulcher/bagger). I think the engineers went into the middle of the spectrum for it. Which fine, but sometimes it cuts my grass a little ragged (tears it) even with new Kubota OEM blades. Versus my lawn tractor that I know spins them blades a heck of a lot faster and it cleanly cuts the grass.
My neighbor who has a KingKutter mulcher also has a very good BTS when cutting normal height grass. If it is too high,the BTS obviously slows, and starts tearing the grass up. This is on a NH TC35 with a KK 72" mulcher.
I know in a year or two when I go to upgrade from my BX, this is one of the key aspects I am going to be looking at when I buy a rear mount for my bigger tractor. Woods and KingKutter are great brands, but I liked the results from the KingKutter versus the Woods.
My
Woodmaxx flail mower does a great job too, again, as long as the grass is at normal height. I put the Kingkutter first, the
Woodmaxx Flail second, and the Kubota MMM a third.
Now about cranking the RPMs higher, if you can, 100 more RPMs than 540 (640) won't do too much harm. But change your gearbox oil out routinely and grease them u-joints on the PTO shaft. Just keep an eye on things, and don't do anything that you will regret.