I am going to go out on a limb here and say that the H9 has a theoretically brighter light but the bulb has a shorter life than the H7. Because the low beam H7 is always on (in US models) it needs a longer life span than the lesser used high beam H9. Having only 300 miles on my new 2018 I have had little chance to test my lights but the one time I did I found that the high beam added nothing to distance or brightness but did light up the sides more. I shall be gathering the necessary tools for headlight adjustment in the near future and going to a dark deserted road and play with my lights. I do this with every bike hoping for an incredible difference between low and high beam and always end up disappointed.
Last edited by jack d; 01-08-2019 at 08:45 PM.
Reason: additional info