I'm gonna go with what they are saying.
I have 4 12"s in the back of my EX, and yeah let me tell you they hit ridiculously loud, and all is well. But it's missing the tight punch that 10's give. While 12"s are great for putting out some major sound. The 12's are great for like rap/r&b stuff like that, that was made to actually feel/showoff the bass. When you listen to punk, or alternative, the bass gets a little I dunno sloppy. It's not really noticeable unless you're into speakers, and such, I would say, and you really know the difference.
So, here we go 12's are great for blowing up the place with boom, and 10's are for a tighter, more clean sound, through all types of diff music.
There are times I wish I would of gotten 10's instead. But when I go down to the local hangout, where all the cool kids blast their systems for bragging rights, I'm glad I have my 4 12's, puts them all to shame.