Now wait a second. Arthur posted a good two-three paragraph reply and I did not see the word " momentum" mentioned once.
You feeling ok Art?
I agree with Arthur. The lighter arrows might not be carrying as much momentum though they might have more KE when comparing your old bow setup with your new one. As Arthur stated I would like to see what you can do with the heavier arrows on your new bow.
Or better yet, go with medium weight arrows and get the best of both worlds.