Here is a local product and for really rough stuff the can not be bettered.
Most rotary mowers just chop the tall stuff down and throw it out.
Flail mowers tend to grind up the clippings turning them into high quality mulch rather than useless smelly thatch.
They also do not leave piles of clippings that purtify rather than decompose aerobically.
Putrifing clumps do not get hot so all of the seeds have the capacity to germinate thus making your weed problem worse.
Aerobic decomposition generates a lot of heat will will kill some of the seeds preventing germination and reducing the weed problem.
https://www.paddockmachinery.com/collections/home-garden-acreage-products/products/atv-slasher-mower
Note on this video how the discharge happens, no tossing grass 30' along with sticks & stones, it just drops to the ground directly behind where it was cut
Rammy do an up front unit which is great as you can actually see where you are mowing and where your are going at the same time
http://rammy.fi/en/rammy-flailmower-120-atv/
Quad X are also popular down here in places where blackberries, lantanna and even native gums are a problem.
Where I am gums can get to 15' tall and 4" thick in less than a year, Blackberries will grow 6' tall and lantanna will grow thick enough to stop a truck.
http://www.quad-x.com/machinery/flail-mower/
It is your decision but I have never known anyone to trade in a flail on a rotary, but there are a lot of used rotaries sitting on the floors of the shops that sell flails.