When it comes to leading with your product or opportunity, I find that both approaches work. It all depends on your prospect. When prospecting, find out what their dreams, goals, challenges, and problems are. Then you can decide whether to lead with your product or opportunity based on which one would most help your prospect. If they are having financial issues, you might lead with your opportunity. Or if they are having a problem that your product could solve, then lead with that. Basically, find out what your prospect's problem is and lead with whichever one can solve their problem.
With that said, I agree that it is important to become a raving fan of your product. If you don't believe in your product, you're not going to sell as much. And if you create a culture of raving fans with your customers and distributors, you will have even more success.