MDJOHN, I have a Kubota
L4600, I have 150 hours on it and have been very happy with it. I have 140 acres with 40 of that being hay/fields and the rest being woodlands. At times I wish I had gotten the MX5100 or maybe even bigger like the M5640, but for my use, the
L4600 is a great choice. It is a good trade off between power and size. It is more nimble in the woods and on trails than bigger tractors, but obviously this means not as heavy and powerful which means slower in the field. If you will not use your tractor in the woods and will only be using it in the field, by all means bigger is always better. If you plan on using the tractor in both arenas, then it muddies the water up a little. For bush hogging, either the
L4600 or the MX5100 will do well with your acreage with the MX5100 having the slight edge on HP. For minor tillage like for game crops or large gardens, either one would do well with the MX5100 being heavier and pulling a little better. If you're working the dirt in all 40 acres, the
L4600 and MX5100 aren't big enough to be an efficient use of your time and you should take other's advice and go bigger. I can't speak much for haying, but it is my experience this would be at the upper level of what these 2 tractors can do with the obvious edge to the MX5100 based on size, weight, and PTO HP.
Take this for what it's worth, the
L4600 was my first tractor because I am a newbie as well. There are a lot of people on this forum that have forgotten more about tractors than I could ever hope to know. I went Kubota over JD based on reviews, recommendations of some good friends, as well as the deals Kubota was and JD WASN'T making. Comparable tractors for me 2 years ago were $4,000+ more for the JD plus Kubota had (and still has) 0% financing. Obviously, both brands are great and you would be getting a great tractor whichever one you choose. If you would like more information on the
L4600 or the MX5100, private message me and I would be happy to share what I know.
Good luck.