"Said" is close to a non-word: we notice it when we write, but readers will buzz past it without registering it, focusing on the dialogue instead.
When you use other dialogue tags, you run the risk of misusing the tag, confusing the reader, or just plain distracting from what's actually being said.
The exception is when the way something is said alters the meaning of the words spoken. For example: "I love you," he sneered.
Source: http://jwtroemner.blogspot.com/2013/01/the-return-of-said.html