The way I look at it you already have the ugly JD.
Don't go out and buy things you don't need and try to justify by saying I will just get more yards to cut.
If all your doing is a few yards in your neighborhood then I think what you have is just fine.
To answer your question the JD is an ok mower for doing a few lawns, but the ZTR is a better mower to use if you're trying to build a business. With a ZTR you could cut your mowing time in half.