Is one better than the other?
I've noticed that national banks seem to charge more (and higher) fees. Is that just me?
George's answer is excellent.
To expand a bit on "which is better", just based on my experience with a handful of regional/national banks and a couple different credit unions:
What's "better" or "worse" depends on which of those things above are more important to you.
Basically, it's a bank owned by its members. For the purpose of your question, regarding fees, you may think of a credit union as a "non-profit" bank.
Credit unions may also be thought of as being similar to an utility (or other) cooperative.
To expand a bit more:
A bank, whether privately or publicly owned, is a capitalistic undertaking, intended to make money for its owners. A credit union is a more "altruistic" endeavor. They can not operate at a loss, but their reason for being is less about profit and more about helping its depositors; who are all part owners.