what kind of music do you listen to?
that should be your main reason for what kind of box to build. generally rap is either ported while rock and country is more sealed.
sealed will give you more of a flat but crisp tight feel, good for guitars and drums
also subs tend to run a little bit hotter as they are sealed in a box ant cant breath. sealed boxes are usually smaller than ported as well.
ported boxes have more of a rumble to them and are a little more loose feeling but can get a heck of a lot louder. downfall is you usually have to run a slightly larger box than if you were to run the same setup in a sealed box. they also have a harder time keeping up with fast rock songs..
i have had three setups all ported but not i am starting to listen to more types of music other than rap and am considering doing my first sealed setup soon