The definition of "success" is different between a bootstrapping business & a VC funded business. A consultant can define success as "making enough money to live off of". A VC funded business has a different definition.

So how would a study be conducted? A survey asking if the business was "successful"?

Actually, that's not a bad idea. Surveying founders at 5, 10, and 15 years after founding whether they were happy with the outcome could be enlightening. A little bit like the 7-up documentary series. It would be very interesting to see which path tends to provide the best outcomes according to the founders.

Maybe for some of them just getting the VC funding is success. Pay yourself enough, last long enough, make good contacts... And if it fails, start over with the extra experience and contacts, or join an existing startup at a high level. Failure doesn't seem to hurt the careers of executives that much.