I don't know about walk behind lawn mowers, but my brother in law has a commercial Cub Cadet zero turn and I have a Toro ZTR (purchased from home depot). The internal parts quality like the engine are pretty much the same. Just a slightly bigger engine of the same make. They even use the exact same air filter. The differences is in the outer shell. No plastic on the commercial unit, has a larger cut diameter and an engine guard is standard.

I don't think it matters all that much for a residential cut, but I do take pride in the build quality aspect. Reminds me of my older John Deere (residential) riding lawn mower. But my older JD even has a superior engine to the commercial unit. They don't make residential lawn mowers like they use too.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne