Actually neither one is necessarily a predicator of success for entrepreneurs.

What is essential for an entrepreneur to succeed is to have a deep insights in the business or domain of the problem they're trying to solve. Insight comes from experience but that doesn't mean a job. Its the deep insights that would help you carve out a value proposition that makes your offering better than others.

For certain types of problems, ofcourse having worked somewhere that showed you the inside-scope of how things work would definitely be required.... e.g. for something like priceline.com having deep connections in the travel industry would help you negotiate the best model that may make your prices cheapest.

But for other types of ideas that insight could come from academics / research (e.g. something like wolfram alpha), or could even come from personal hobbies or odd jobs that you did earlier in your life that helped you understand the dynamics behind something.

Lets say you wanted to start a music label for orchestral music - would that really require work experience in that field, or just a passion for it that you've been exploring on the side for many years?

The other part is about being able to aggregate appropriate resources around you for the new company.

There again - depending on what it is you want to do and what type of resources are essential - you might have an edge with either deep connections with decision-makers, which could come from experience (hopefully with the right job too), or your edge might be with how many people who relate closest to your target customers you want working with you.

E.g. if your offering targets students, or freelancers, the right question to ask is how easily and willingly could I get other freelancers or students to help me with our vision.

In those two examples - students and freelancers themselves are best able to attract other students and freelancers towards that business or vision - and that's very hard to do for others.