I'm not sure I understand the power requirements of your task so can't advise anything specifically. For my field, which I cut only once a year and which is full of saplings every fall when I cut, even my medium duty cutter takes a beating, but that's what they're built for. I'm glad to have the ability to cut a tough field with a 6' cutter.
I have an MX5400 which is 20% wider than an
L3901, and that was important to me for navigating my very hilly terrain. The pros and cons are the same, it's bigger. That's good if you need to move something heavy, bad if you're trying to navigate a tight forest trail.
Mostly, on the trail thing, the one thing I didn't plan on in restoring my forest trails were the huge stumps the last logging operation left behind. A tractor is no good for stumps (unless you have a stump grinder), and so they're a major impediment for my navigation at present. Just something to think about.
Other than that, I was concerned that I was buying a level higher than I needed. But when my tractor is struggling with some of the heavy things I try to move, I'm really glad I didn't buy anything smaller. Whether that's disloging rocks, moving trees, or a heavy load of gravel in the bucket.
As others have said, you can manage an MX5400 for 40K, depending on your attachments, if you don't have a cab. Mine was about 45k (can't remember how much of that was taxes) with filled tires, heavy duty bucket, medium duty 6' cutter, grapple, third function hydraulics, pallet forks, heavy duty rear blade.
Caution, if you need to haul your tractor, note the weights of things. My tractor, with loader, bucket and rotary cutter, is nearly 4 tons. I can't haul that with my truck. A lot of people don't consider that when pricing. I can work with that, for example the Kubota dealer did my 50 hour check at my house.