They're (Helo's, jets, 130s) all baddasses to me, so none and all of you win according to my poll <sniker>.
The Navy gets the new equipment as far as jets go, so if you're a "I have to have a jet" kind of person go Navy and be the best in your class. I think it's both difficult.
I may be wrong, but Navy puts emphasis toward acedemics, and Marine Corps toward physical. Don't get me wrong you gotta have a degree in both cases and pass all the tests. Both also require PT just a little less stringent in the Navy as opposed to Marines.
Also, if you got arrested for something when you were a kid (ie. assault with a deadly weapon) the Marines are more likely to waive it than the Navy. This is just my speculation since I never applied Navy.
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Semper Fi