1080, only because it's a challenge to find a good 720 at 40+ inches - once I set the fire tv up, I looked and realized that the time for new large sets at 720 looks as if it ended in a war of pixel counts five years or so back.
Since we can only vote once I have a 1080 and 720. I have an awesome older 720 JVC DLP that I plan to use until it melts because of the awesome picture.