I think a large frame would be too much for these needs. I have had both, most recently a 4520. To me, the large frames are much more machine than the mid frames. They do more, faster, and have a lot more power--BUT--there are times I miss my 3720. It was a really stout tractor, and I am now wondering whether to attempt to buy a RFM for spring with my new tractor, or to get something small for specifically mowing. The 3720 with a rear mower was the ticket, and did great. I think the 4000's are a smidge too heavy for treading lightly on grassy areas or in landscaped areas where the ground may be soft. They would do fine, the ground might not. In short, if you have big projects that require big power to complete, go large, if you primarily want something that can get around in tight spaces but still has enough weight to do heavier work, go with the mid frame. My neighbor cleared 7 acres of SOLID woods with his old 4410 (mid frame) and it did fine. He now has a 4320, and thinks it would have done it in half the time.
John M