B-billets: Do a search on that and you'll have enough reading material for a week on the can if you print in out.
Aircraft:
www.usmc.mil has an equipment "factfile" that will detail all our birds.
Deployments: It used to be a pretty regular pattern, but recent world news has destroyed the cycle. Expect to be on the boat or in the field a whole lot.
Comparing vs. the Navy: I chose Marine helos over jets, and yes, I did have the primary grades to do either. The mission absolutely rocks. Assault support is very cool. Having a squad of grunts in the back, at night, at low-level is a very cool feeling. Doing CAS in a Cobra or Huey would also be a great deal.
If I were in the Navy, though, I would've chosen jets. Vert-rep and sub-hunting doesn't exactly have the sex appeal of formation flying on NVGs. They do some interesting stuff hunting surface craft and some SEAL support, but that's the exeption, not the rule. I think that is gradually changing, but it's not nearly the same tactically oriented environment.