Can someone tell me the difference between a box that has the port facing the interior of the car with the subs facing up, and both the subs and port facing the interior of the car? I have seen the former in a few videos (yes, crappy source)

Pros and cons of subs and ports on the same plane ?

My car (bmw 735i) has good insulation between the trunk and car interior. The subs will be upfiring (if I go that route) into the back of the car since they will sit beyond the windshield.

Thanks everybody.

Oh last question -

If the subs upfire, are the L ports positioned differently? I had thought you would simply mount them on top instead of on the same plane as the ports and keep the L bracket the same, but on second thought seems like there should be something else done

Unfortunately I can not "try them both" since I will be building this box. Which is why I am trying to decide beforehand.