Back when i was about to start primary flight training, a Harrier dude flying for the Blue Angels told me "go jets. Remember that there is a program for helo guys to transition to jets, but it doesn't go the other way." As far back as I can remember, there hasn't been a single hornet guy to go to helos. But I can think of at least 5 helo guys in jets right now.
If you are already a Marine, do what it takes to get to flight school and then work your butt off. If you have jet grades you can get anything. If you don't make the jet cut, you won't get jets. Period. Finish number one, you will probably get your choice of jets or helos. Finish number one in Kingsville or Meridian (jet training) and you will probably get Hornets AND your choice of coast. Lifestyle is about the same in the Navy or Marines, lots of deployed time. You may be unlucky and spend you time MOSTLY deployed. If that bugs you, don't do it. A carrier deployed hornet guy will spend 9 of 12 months deployed during a deployed year, and then home for 6 months or so before the cycle starts again with CQ's, and work-ups. That will be for 3 years, a break of some sort for a year or two then back to the squadron again before your contract is up. Hope this helps.