I have a feeling that Garmin is only looking at the Music version when it comes to the battery consumption.
I have a non music Garmin 245 which after SW 3.90 and now with 4.0 it still consumes 40% more battery! Same conditions, same apps installed.
Before I used to get 7 days of battery with 0.500%hr and now I am in the higher 700-800 %hr
This is a 40% increase.