Ported is usually bigger, and if you have one built for you, usually more expensive. As far as sound is concerned, a lot of people will say that a ported box will be boomier, but if the box is designed and built right, and tuned to the right frequency, it can sound every bit as good as a sealed one.
Alot of it depends on the speaker you're using, as some just don't like being in one type or the other.