sealed will require more power to run simply because of the restrictions of airflow. You can achieve spl with a sealed box to a point? Thats debateable too
ported is where it's at as far as i'm concerned for spl or sq. A properly designed port can sound good in just about any application, and yes it will require more cubic ft for your box, but in the end it all depends on the room you have to work with wether to port or seal your enclosure.
Sealed boxes typicaly will be more acurate thoughout a broader spectrum of hz....20-80hz .......ports are usually tuned to make one specific frequency louder than the rest. If a ported box is tuned to 60 Hz, 40 or 80 Hz won't be nearly as loud.