It depends on what your situation is.
If you're trying to build credit and not deal with all sorts of hidden fees and premiums a Credit Union may be the way to go.
The thing you need to realize though is:
A Credit Union isn't a profit-making entity. Therefore, they are NOT going to have the customer service you would expect from say, a Chase Bank. So, if you have any issues on a Saturday, it will have to wait until Monday.
The good thing about a Credit Union is that it will not allow you to overleverage yourself into a bad situation. I needed a loan to purchase a car in 2010 and they were adamant in making sure the loan did not exceed a certain percentage of my income. Whereas a commercial bank would have loan me more, but at a higher interest rate.
It depends on your needs. If you do a lot of banking and traveling, I would suggest a commercial bank. If you're trying to build credit and be a bit more conservative on your finances, a Credit Union may work for you.