The first answer that comes to my mind is money. People are competitive because they want to make a lot of money and have all of the things that come with the money. But I think there are people who are competitive simply because they like the challenges. Some people get excited about making a sale. Other people love the deal with problems and solve them. Some people will spend a lot of time working with information and deciding what it all means. I think they are not competitive just to "beat the other guy" -- they really enjoy a challenges of their work and, as a result, they do better than their colleagues and find advancement in their careers.

both experience and diploma are important, in my opinion.

and a skill of liking someones arse of course. Experience, experience and experience. Also you must have a portfolio of your works (if your profession needs it).

Their qualifications mainly then the ability to make the best use of those qualifications in a competitive surrounding.

If you are good or not. If you have experience or not.