Sit on either window side of the plane, one in front of the other. Ie: on 787 4+5K or 4+5A. At the front noise from toilets, at the back noise from the bar.

I'm not sure where the snooze zone is on the 787.

Sitting across the corridor from each other is actually quite far apart (not been on 787, but true of 747/A346/A343), so one in front of the other is best.

On the 747, avoid upstairs its the snooze zone, and also its actually in front of economy passengers, so the priority exit of the flight is affected (you'd at least be behind Upper and PE passengers).

I'd favour the front cabin on 747, with the same sort of choice, 16/17K A or K.

Some people like the 12A/K, because they are closer to each other, virtually touching feet, however, I don't like them because they are actually at more of an angle to the direction of travel than the other seats (affects 13 and 14 a bit, but much less so). If you get travel sick it might affect you more. I'm not sure I've ever had the choice though, there's always someone booking them first...