Does it convert better? Amazon said as long as the user puts the product in the cart and places the order within 90 days, it will be a valid referral.
under "performance tips": Add-to-Cart Buttons. Provide your visitors maximum convenience by automatically adding products to their Amazon.com Shopping Cart when they click on these buttons, enabling them to skip the process of going to the item's detail page and adding it from there. You will receive credit for the purchase as long as the customer places their order within 90 days. To learn how to build this type of link, click here.
The cookie duration is set to 24 hours, but the customer can add product into cart (after clicking on your link) which is valid for 90 days.
My personal experience is that it is better without the cart as far as conversions go. As far as making it look professional - of course that's another story.