I would go for 787 regardless of the airline. Because 777-300 is old and noisy and has to be decommissioned. The most important difference is the cabin pressure and humidity, which are higher in 787 (and A350/A380) compared to 777, so you will feel much better after the flight. For the very same reason, I would prefer A380 to any Boeing -- the upper deck in A380 is very quiet.