I can see where a wider cutter would be handy as mentioned. As long as you remember that it's sticking out /forums/images/graemlins/crazy.gif. A narrower cutter may not work as well because your tires will press down grass that is not lifted again by the cutter.
I love the fact that my rotary cutter, also my box blade, my front and rear tire width, and my bucket are all exactly the same - 48" (TC18). If my bucket is close to but clears a fence post, my tires and cutter will follow exactly the same path. When I use my 6' landscape rake, occasionally I forget how wide is is and hook it on something. Same with the 6' root rake I made for my bucket - the other day I was using the box blade around some fence posts (before I put up the new fencing), pushing the weeds and dirt mounds backwards, while watching behind me, went a little too far back, and took out a post with the root rake. Oops! Then, a few minutes later, I did it again! /forums/images/graemlins/blush.gif I muttered to myself, got off the tractor and took a break, then climbed back on and managed to remember for the other 75 posts. Based on my track record, if the mower was wider than the tractor, I'd probably be mowing down all sorts of things I never intended.