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.
he's right about the ported box....it will be bigger.....and building it takes more time...and it a bit more involved. sealed on the other hand is the easyest,smallest,most widely used. when built to specs...you really can't go wrong.
if you decide to go with sealed...it'll be cheaper,the sound will be an all around sound..meaning you can listen to anything from country to rap and it all sounds good. ported on the other hand...would be a bit more money if you had somone build it for you,sound from a ported box would be for the one who likes alot of boomy bass.....as joker said..if tuned right..will sound great.
as goes for everything,all it really is is personal perference. find some shop that can demo boxes and subs...so what you like best then go from there.hope this helps.
The problem most ported enclosures run into is that people build them without understanding tuning frequencies, and end up tuning them way too high. If built right, like said above, they're usually louder and can play lower than sealed setups. Like Joker said, though, it depends on the driver. Some work great in ported, but others sound much better sealed.