I don't know if this applies to you but in my orchard I wish my tiller had substantial offset so I could till close to tree trunks without running my head into the limbs. I think offset is a feature worth paying a little more for.
Of course for open ground offset would be irrelevant.
I think our farming here is unusual. No rain from Easter to Thanksgiving, to oversimplify a little. Everything has to be deep rooted to survive. My neighbor who commercially operates/harvests this orchard for me says he has found what works best is he discs once a year in early May when the grasses dry out and turn brown, to turn under the native grasses and cover nitrogen crop he planted last fall.CA - If you're under the limbs with a tiller, aren't you tearing up your roots? I always thought most trees have a root system about the same diameter as the tree itself.