As the others have said, it's probably better to run the highest, especially if you're installing it for potential need / safety vs 'just for fun'.
If something happens where you 'need' the footage, having better resolution may make the difference for you. In those cases, you really need the last few minutes of recording, so no need to worry about saving more than 15 (?) min or so, and just overwrite as needed (if it has an option for 'overwrite on powerup', that's convenient, but be careful if it ever records something you need to keep!)