Both ships feature identical facilities with activity itineraries that are likely very similar.
Adventure Ocean coordinators have control over the activities and when they are scheduled but in 10 years of cruising the activities onboard all ships from the smallest to the largest are relatively the same.
A RCI youth staff member whom I'm friends with on facebook (was one of MY teen directors on the Sovereign of the Seas) is currently working on the Oasis and unless anything has changed, she's an absolute blast!
Either ship is a great experience, though, having personally sailed on both, I prefer the Allure to the Oasis. The newer ship has different dining options, and better entertainment options compared to her older sister.
Any questions- ask away.
Ryan- The Cruise Encyclopedia
Oasis of the Seas
Allure of the Seas
Freedom of the Seas
Mariner of the Seas
Navigator of the Seas
Grandeur of the Seas
Enchantment of the Seas
Monarch of the Seas
Voyager of the Seas
Sovereign of the Seas
Cunard Queen Mary 2
Cruise Total as of March 2012: 100 Cruises
I've noticed that the activities that take place in the actual club (Fuel) tend to be the same on every RCI ship. What aren't the same are the activities that take place on other parts of the ship. For example, Allure of the Seas might have Teen FloRider time or Teen Ice Skate time, where as an older ship like Majesty doesn't have either of those. Also, ships like Freedom, Allure, Oasis, etc. have the Living Room, while other ships don't.
I went on a 3-night Monarch of the Seas cruise this Feb. and I have the teen compasses which I can email you copies of if you want to see the kinds of activities that take place in the club!