If an affiliate changes the terms of its program, your revenues could be directly affected. Choosing the wrong affiliates can also be problematic if your blog or website audience doesn't feel compelled to buy their products or services. With the affiliate-marketing industry experiencing a boom, you’ll also have to contend with competition from other marketers shilling the same affiliate products.
Affiliate marketing will give the better opportunity to make the most money. AdSense will make you smaller amounts of cash regularly with very little maintenance. However, it needs a fair amount of traffic to be really profitable, while you can use a mailing list to sell your affiliate products. You can build up a large list over time, even with a small amount of daily traffic.