I'd say go for the op3. P9 is a bit overpriced for what you get. The loud speakers on both are standard, on the bottom, nothing special or particularly wrong.
Op3 is better for rooting and custom ROMs
Its better for sunlight legibility (thanks to amoled)
And it has cleaner software (close to stock), and better performance (better chipset and overall seems to run smoother)
But I think p9 takes slighly better photos