The discrepency is sad, but it's a little like comparing apples to oranges. Boy's Life is the official magazine of the Boy Scouts of America - you get a subscription as a member of the BSA. It's been in publication since 1911, and doesn't need to pander for subscriptions, or sell itself in the check-out line. Girl's Life is the product of some publishing group starting 1994 to make money - it needs to convince people to buy subscriptions or make that impulse purchase.
From a quick search, it doesn't look to me like the Girl Scout's currently have a comparable magazine for members. If it did, that would be the ideal comparison.
Not saying that society isn't teaching gender inequality - I recently had to have a discussion with my 4 year old daughter that yes, boys can wear pink (a topic brought on by the NFL breast cancer awareness campaign) - just that this isn't a great demonstration of it, though it would appear to be on its surface.
EDIT: I see there was once a Girl Scout magazine, first called The Rally, then The American Girl, last published 1979. Here's some of their old covers. It involves some gender stereotyping as well, but at least I see some covers depicting archery, canoeing and swimming. Considering the time period, I suppose we could consider that fairly progressive.
There's also covers from a more recent, unrelated magazine called American Girl; just disregard those.