I agree with what a lot have said. However, not many have talked about the Surface Nuclear community. I am now on my 4th tour on a Nimitz class carrier. I just left shore duty in San Diego working on Subs for 3 years, so I have gotten to know thier routine and can honestly compare them.
First thing to remember, you can volunteer for Subs at any time during the training pipeline, but once you volunteer, you can't undo it. Wait till you get to prototype before making that decision. This way you will meet both Sub and Surface instructors and be able to make a more informed choice.
Right now on my ship, EM's have the best routine because the entire surface fleet is overmanned with them. It is not uncommon to see them leaving the ship prior to 9am when in port. ET's are not too far behind. MM's work the most and have the dirtiest jobs to do.
That being said, I think MM is probably the best rate for long term advancement in or out of the Navy. By the time they are Senior in Rate qualified, they are already done with 70%-80% of their Watch Supervisor qualification. ET would be second, followed by EM (if you want to stay in the Nuc Field). EM's learn a lot of Power Distribution stuff, but that doesn't really help much with Watch Supervisor Quals or, from what I can tell, the Civilian Nuclear Industry.
The EM joke is we are smart enough to turn switches and strong enough to turn valves, but what I think really happens is you get someone that is a dillitante in all things and an expert in nothing (I am proof of that
As far as Sub or Surface, Having seen what the Sub nukes go through, I am glad I am on Carriers. We have just about 100 Nuc EM's and we only deal with the propulsion plants. We have Conventional EM's to fix all the other stuff on the ship. We are in 5 section duty vice 3 for subs. I have been to Naples, Rhodes Greece, Corfu Greece, Rio De Janero, Valapariso Chile, St. Thomas, Hawaii, Yakuska Japan, Hong Kong, Singapore, Dubai UAE, Muscat Oman, Hobart Tazmania, and Perth Australia. I don't know too many Sub guys that got to see all that. Their is also rumor that a Nuclear Carrier will replace the Kitty Hawk in Yakuska Japan a few years down the road, so Nucs may have a chance for Overseas tours in Japan.
Hope that helps,