Basically the Short answer is this...........
Go for what ever sounds best to you. No-one can tell YOU what sounds good to YOU.
If you like the Punch from 2 10in Subs then go for that, Or if you think that 12's sound sweeter then that's what you want.
Personally I have always prefered the Low Rumble from a 15in, but that may have to go by the wayside when I finally get my 34 (Space may not allow it).
The general rule of thumb is the smaller the speaker, the quicker it can react to signals.
The Choice also depends on the type of music you will listen to.
Hopefully this may have given you something to mull over.
If all else fails, Seek help from a Professional.
