Hi Cindy,
It really depends on what you hope to accomplish - what your main objective is. Many people use the "name squeeze" method on their landing pages to build a highly targeted opt-in list that they can follow up with via email. Once subscribed, the visitor is redirected to the sales copy. If they dont convert on that first visit, the site owner (or affiliate) has an opportunity to follow up with them and encourage the sale.
Others use landing pages to pre-sell the product/service they are promoting. As an affiliate, many people will post a review or will highlight the features & benefits of the product. You may be appealing to a specific market, where the sales copy is more general, for example - and so you use the landing page to pre-sell this product to that particular market.