[bpsooner]

When I was looking for a tractor, I had the same types of questions that you have. Some advice was given to me that really helped me make my decision. Purchase a tractor based on your current needs and possible future needs.
If you are needing a grapple bucket and have projects that require it, I would get a tractor that can handle it. You do not want a year from now needing that larger tractor and having to look for another one. You do not want to regret your purchase.
If you can possibly afford it I would recommend purchasing the 4120. Having too much tractor is always better than not having enough...