BillFires, There are several B21 owners on this board and I'm sure they will be happy to add some thoughts.
First on the down side, mowing with the B21 is probably not in the cards. It has no mid PTO and the loader is not designed for quick removal. With a rear mower the loader limits your manuverability. The PTO horsepower is 13.5, which is on the low side for compacts. I run a 48" rotary cutter and 50" tiller just fine. The warranty for the B21 is only 1 year. I guess they figure is you buy a B21 it will see commercial duty./w3tcompact/icons/frown.gif
On the up side the B21 is a tough little tractor. The hydraulics on the B21 are pretty robust, with a 8.5 GPM pump and ~ 10 gallon reservoir, you can work it hard all day long.
Pulling stumps. Thats a tough one. I have seen D7 Cats pucker up on stumps and it doesn't even take a big one. I have dug out big Maple and Cedar 2-3 ft Dia. Just takes a while. Smaller stumps 6" to 12" no big deal, but still not a slam dunk.
If you really want a backhoe the B21 is hard to beat. You might also look at the L35.
Al