Many folks laugh a bit at the USMC claim "Every Marine is a Riflman" but it's true.
I'm one of them who laughs at the claim.
In most armies the clerks, supply types, and truck drivers have probably not fired their rifle in months, if not years. In the USMC EVERY Marine is required to qualify with their weapon yearly
That's because the USMC can afford to have it's logistics handled by either the US Navy (when they do amphibious landings), or by the US Army (when they're Army Junior, as in Iraq); so they look like they have a very high tooth to tail ratio.
Don:
Morale can be between +5 and +10 higher on average, again, it depends on the decade. And that was done years ago to make them " More special"
I've run across some very interesting statistics from past yearly annual DOD reports, they make for interesting reading; this is from the FY79 report
Desertion rates are a good eye into the "morale" of personnel, and it's very interesting to see that the USMC always has higher desertion rates than the Army; and it gets very pronounced in the late seventies; where the army goes down to 1.77 per hundred in 76, while the mAarines are at 6.92 per hundred.