2 super 12s > 2 15s. The 15s box may need to be built in the trunk which for someone without a ton of experience leads to mistakes fairly quickly. Also they may not be getting as much space as they really need, choking them is a bad idea. Also, with two 12s most people can seal them off firing forward which will make it that much louder. Very few trunk cars can do that with 2 15s. (fucking sucks I know, thats what I wanted to do )
Also, alot of those setups have to fire the subs back towards the trunk lid or up into the trunk lid. Idk about your car, but that would probably tear my civics trunk off.