That's a tough decision. You can do a lot with a tractor you can't do with a ZTR. Front end loaders are great for a lot of chores. ZTR will mow in about half the time of a tractor but that is all you can do with it. The wife could easily drive the ZTR they are easier to mow with than a lawn tractor. Once she gets used to it whch doesn't take long she will might just enjoy it. They don't handle steep slopes all that well depending on the ZTR. Get a dealer to bring one out for a demo and put your wife on it after you get familiar with it.
Snapper S50x 36" Deck
Shindaiwa EB212 Blower