I've heard that a 30g is recommended for adult bp's. I'm considering downgrading from my 40 breeder to a 30 due to some stress issues. Which 30g is the better one?

30 Gallon 36 x 12 x 16 (LxWxH)
30 Breeder 36 x 18 x 12

These are my current tank dimensions:
40 Breeder 36 x 18 x 16

Thanks!

(I forgot to mention: I would prefer not to go to a 20, as I think I would need to upgrade again in the future. Plus, most of my current stuff would not fit in a 20.)