In the end it really doesn't matter at all if you make your wine from a kit, in a UBrew store, at a vineyard you visit or just buy the wine pre-made. All wine comes from grapes - and it is those grapes that provide the health benefits. That and the alcohol

The resveratrol comes from the grapes, not from the fermentation time or anything else. Resveratrol is an antioxidant, which I'm sure you've heard about as being very good for your system.
The American Cancer Society did a study of 500,000 patients. They found that those who drank 1-2 glasses of wine each day had a 20% less chance of death.
Anyway I have a ton of pages on wine and health -
but the basic gist is that the benefits come from the grapes, and from the alcohol. Any grape wine you make, whether from a kit or in a shop or at a vineyard, is going to be made with grapes as the raw material. So you're all set.