Neither. The goal of the show is to promote business and entrepreneurship. That's why Lord Sugar does it; it's not so much because he wants personal publicity, but because he's devoted his life to business and wants others to do the same. It's partly self-validation and partly what he thinks is best for this country and its population and the potential entrepreneurs themselves.

So ideal winner will serve with Lord Sugar for a few years, learn what they can learn, and then leave and set up a business of their own. They will become their own boss. If they remain with Lord Sugar as their boss forever, then they've failed the spirit of the show. The winners who leave after a few years are the success stories.

If there's a reason that Michelle shouldn't have won, it's that she was too good. She was already an entrepreneur, had already created her businesses, and didn't have as much to learn from Lord Sugar as she'd hoped. Several other people have failed to win for the same reason: for too much prior success. (James in series 1 springs to mind.) It undermines the show as a competition, but fits with its real ethos.