"Construct a list of the most successful technology startups however you like (by revenues, market cap, number of users), and you'll find the number that didn't take outside funding is zero or near it."

I think looking at how much money the founders made would be the most objective measure. Of course you're going to be able to create a bigger company if you go out and raise a few million bucks, but that doesn't necessarily mean that you'll personally be better off in five years.