only difference is if they have there own compartment and 1 blows urs still good cuz the sub has the proper box volume, with one big box and u blow one sub ur pooched, thats about it. im running 2 15's for spl and i just went with one big box not for any specific reason. its mostly preference. try not to overdo it with bracing cuz it cuts down air flow in the box and reduced air movement, depending on the shape of ur box u may not require much bracing