What's the best kind of small walk behind mower to buy? I'm talking just a 21" or so for those tight places you need to trim. I had a 21" Yard man...best mower I've ever owned and I put it through hell. Not a big fan of the Briggs and Stratton although this one did me well. What's your opinion? I have a gravely 36", so I won't be using the 21" much.