(For the purposes of full disclosure, we only do residential lawns.) I've been using the 21' for a couple of decades - off and on - and am so comfortable with it it's almost second nature. Am I doing things I shouldn't be doing like wearing shorts and not wearing protective glasses, I don't know, but that's how I learned how to use it. I started reading the manual for the 36" and it calls for long pants and glasses. I started thinking it's just typical "cya" boilerplate until I realized the machine is much more powerful and maybe it's very practical advice. Too bad I work in Texas and fear if I wore long pants during the summer, I'd die of heatstroke before arterial bleeding by a well placed shot of debris. But I think I'm getting ahead of myself. I've always liked the 21" because I'm strong enough to stop it should I veg out and come close to running it off the curb or get too close to a vehicle. Certainly it's light enough to push towards a tree to get as close a cut as possbile without worrying that I'd gouge the tree. With the exception of a few sprinkler heads, I know which ones at which settings I can pass over without concern of lopping them off. If I slipped or fell, it was so simple to disengage the drive. I've never really had to worry about the mower falling on me. I know that the 36" WB will cut a lot more and with my back problemas that should be a no-brainer, but at the same time, a 36" can only cut that which it can get to, so too small gates rule it out. Maybe to jsut cut to the chase, there looks liek there is so much more to learn regarding how to use a 36" vs. a 21" and I don't just mean checking oil levels. And here's more disclosure: I'm not a fast learner. I guess the question I've had for awhile is: can I become proficient using one before I do real damage, either by way of misjudging the distance/slope and laying a fat scratch down someone's car or bending a spindle by going over a water valve cover that never gave me a problem with a 21"? Anyways, I've thought about posting this here for a while and figured it was time to do since we will be ramping up in the next month to start going out again. p.s. - have I ever mentioned that I hate change?