We just returned from a trip on RCCLs Explorer of the Seas. We actually went on this ship instead of the Magic at my DS13 suggestion (the power of advertising LOL). He wanted to try all of the activities as he was bored with the Lab on the Magic the last time we sailed and was concerned with the 13-17 age range (
RCCL breaks the teens into 12-14 and 15-17).
While smoking IS permitted in the cabins, you have to ask for an ashtray and our balcony cabin did not smell of smoke (and I know guests smoke on Disney too, as the burn marks on desks and carpets will attest and our stateroom host confirmed). I have a problem with smoke and since RCCL requests smokers to only use the starboard side of the ship (and I only saw one woman who didn't) I just always walked on the port side to avoid the smell.
We did not pay for milk, coffee, or tea at dinner and because my son had a soda card (only $24 for a week including a cool insulated cup), he never paid for soda at dinner or Johnny Rockets (a fun place to eat on the ship). Never paid for milk, juice or lemonade at lunch or breakfast. We enjoyed the food on Explorer and our waitstaff was outstanding. Never tried the 'ranch steak' as it is an alternative selection and we always found something we liked on the regular menu. The requested dress code also seemed to be adheared to more on RCCL...lots and lots of tuxes/dark suits and long gowns on formal nigh (which we enjoy).
Never saw the casino..you can walk through the whole ship and never have to pass through it. RCCLs arcade is much bigger than Disney's, much to DS's delight and it's right next to the kids club so he was always in 'the neighborhood' if I was looking for him.
The soft serve ice cream was the same as Disney, as far as I could tell. You could purchase Ben and Jerry's if you wanted but we had no need. Also loved the 24hr Cafe Promenade with pizza, sandwiches, 6 kinds of cookies and two kinds of cake available for the asking.
I found the adult pool area was strictly enforced, in fact, they have glass doors which separates the adult Solarium from the regular pool and my son wouldn't even walk through them. They do allow 16 yr olds in the Solarium but the ones I saw in there were always well behaved.
Not sure why the shows are considered Vegas/showgirls type. They are more of the Cirque du Soleil type, if anything. No Disney characters but that hardly makes it adult entertainment. The Ice Show was the best show I've ever seen on a cruise ship.
I think the Disney ships are wonderful and we would sail on one again if they were less expensive. But since we can only cruise once every two years or so, I have to put my money on the RCCL Voyager class ships. For teens and young adults (under 21) I think they offer more in the way of entertainment and it was definitely not a 'party ship'. I have also sailed on Princess to Alaska and it was an older crowd but still a great time (without kids). This is just my experience...hope your cruise on any ship is all that you desire.