The debate is on which method causes the least damage to hair. If you are the type that prefers to towel-dry you can be too rough and end up tangling it. However, if you remember to just gently blot your wet hair instead of using a vigorous rub, your hair will be spared from damage.
Now, on the other hand, you might be tempted to use a high heat too long when using your blow dryer. As a result, hair can suffer damage and frizz. So be careful and remember to be kind to your hair regardless of the method you choose!