Both pictures give me a page with this picture:
[img]
http://members1.clubphoto.com/_cgi-bin/getImage.pl?imgID=5990612-7fa8&trans=[/img]
But, 50Hz is plenty good enough in a car. There is a cabin gain of about 12dB per octave below 50-100Hz, depending on the car. So, I think the vented will give you a little more output in the 30-50Hz range, at the cost of under 30Hz frequency response. Vented also requires a larger box. Those are the fundemental differences. Sealed is easier to build as well. I guess you must determine if the output with sealed in the 30-50Hz range is going to be enough for you.
Aaron
