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.