It is amazing how the mud can get packed in so tightly. Once got badly stuck on a tractor with duals. It took hours to get the mud out. Had to use the hooked end of a crowbar between the tires and chip away at the mud. It seems the worse you are stuck and the more you try to move, the more packed the mud. If you get stuck and have someone pull you out right away, the mud comes off much easier. The FEL has saved me many times and you can push yourself out.
The best tractor I have owned for mud was a JD 5300 with FEL. Front and rear tires were relatively big for the size/weight. MFWD, and good clearance. That FEL did not have the linkage on the bucket like most CUTs. It could really push the tractor when curling with bucket. My CUTs do not push near as hard. The extra linkage on a CUT bucket is suppose to help with curling power. However, when the bucket is fully tipped down, there is little mechanical power and the curl cylinder is nearly parallel to the lift arms. This is when you need the most push when the bucket is completely tipped down.