It's funny.
Whenever there's a thread about the Army (like, say, THIS ONE), the USMC comes running ;)
If you REALLY ask around, it seems the USMC is overly concerned about the Army. After all, you're here, aren't you?
You want to look at in-theater depolyment numbers to see who's fighting? I'd say both the Army and Marines are shouldering the burden and leave it at that.