Interesting trade for you. Only you know how you will use the tractor....and I hope the 3320 will work out for you. Funny....as this is quite similar to the tractor I just bought....except without the hoe.
I have the same hydraulics to operate my front Markham/Gator grapple. Just finished installing it yesterday. I believe its going to work out pretty nicely. (see the attachments column for pics and install).
I use my tractor similar to you....manage a large wooded piece of land and maintain some food plots near Brainerd....but live in So Central MN. That hoe sounds pretty nice.....
Its more than just the brush hauling although chipping would be an option. Its the smaller tractor's appeal for other jobs as well. Keeping the 4720 and getting another tractor would be nice. But for now I would just prefer the one tractor.
The 4720 sold in about 2 weeks. I have fond memories of the comfortgard cab with all of the snow plowing we did this winter. The "add on" cab I put on the 3720 works but its no Comfortgard that's for sure.