It all depends on what you will/want to be doing.
Just mowing... a Z is choice hands down!
You want to be snow blowing... tilling... pulling trailers etc. an AWS commercial lawn tractor is the ticket. I have both... started with a JD 445 and moved into Zs as the business grew and realized time is money for mowing. I now use both to their full advantage.
Not much money to start with for commercial quality machine but they can be found if you keep looking.