I got my silver altitude gain off of an auto tow. As a CFIG I have instructed at two winch clinics using our winch on a public airport. A well set up, high torque winch, with Spectra, the correct tackle, and a winch driver that knows what he is doing is pretty hard to beat. In my opinion a winch launch is the best option between the two given a choice.

I would try several auto tows with different local gliders, and pilots before I attempted to set up an auto tow weekend event. There are a whole lot of things that could go wrong. You don't want a bunch of whiners from out of town bitching about, while you discover what they are. Oh, volunteer your own vehicle for the towing while you are at it, that tends to alter ones opinion of the event.

To answer you questions in order
-wear and tear on the tow vehicle is a significant cost that's hard to account for.
-It's not simple all the time, say the field is a little wet, the glider lightens the back end, and the tires spin. It can get exciting.
-You have to have the right site, launch crew, and vehicle to make auto towing practical.
-it's not more fun than winching on a good winch. Think Ski boat with not enough engine.

SF