but I want to join the one where it may be easier to become a fighter pilot. Or are they about the same?
This is probably next to impossible to answer. Both Navy and Air Force have challenging selection and training programs, so its not going to be 'easier' to become a fighter pilot in either.
Also, fighter slots change on a weekly basis. Sometimes they need plenty of people for the pipeline, sometimes not...for both Navy and AF. If you search the site, you find an agreement that you will not be able to game or predict the system. There are too many 'well I know this one guy stories...'
Also, would I be able to travel more in the Navy or the Air Force?
In terms of outright travel, as a pilot you might 'travel' the same amount in Navy and AF. However, if you mean see exotic places/foreign ports etc...then Navy hands down.
When I was a Midshipmen, I saw Japan, Korea, Hong Kong, and Singapore before I was 21. No AFROTC guys I know got to do stuff like that.
Which one would I be able to meet more ladies in?
The question is, can you spit game? Saying "I'm a fighter pilot" might get you the opening line (and a lot of ridicule from your peers), but if you can't talk to girls, then your SOL.
are you able to lift weights during flight school (yes serious)?
This is kind of a ridiculous question. Yes you can. However, if you are jacked and don't make height/weight standards then you should adjust your routine.
Dietary supplements, i.e. protein shakes, creatine are severely restricted if not outright forbidden.
Also, since being sent to JSUPT at Vance I have found it harder to keep up with a steady PT program because of the AF's style of training.