Generally you could say:
The greater diameter, the better the low frequencies. So a 12" will be better in giving lowest frequencies than a 10".
Of course a low-quality (!Attention! - I don't say cheap at this point!) 12" could be worse than a high quality 10".
But I think the difference is not that big.

I'm with tony that a sealed box is fine an you don't have a too boooommbastic bass. A sealed box brings a very clear sound and doesn't need a too big box volume.
Every sub can go in either sealed box, bassreflex box or bandpass-box.


TeeMcBee
Got my Mk2! # 080000143