When I have an article on a specific product or service, I typically use an affiliate link. This is because most of the visitors to that specific article are there after searching for more info on that product or service and are thus in "buying mode" for it.
If my article is more general or about a free event, etc. I'll place Adsense code, as those visitors are not typically in buying mode, but an ad may be displayed that catches their interest anyway (maybe interest based from a previous search).
The above works well for me.