Allure and Oasis are 95% identical.
The rest of the 5% in differences comes down to shows and a couple of specialty restaurants - all a matter of personal taste.
They're both spectacular ships.
Allure of the Seas (Western Mediterranean) - May 2015
Radiance of the Seas (Alaska Roundtrip/Vancouver) - 5/9/14
Independence of the Seas (Western Caribbean) - 3/23/14
Adventure of the Seas (Southern Caribbean) - 2/23/13
Oasis of the Seas (Eastern Caribbean) - 2/10/12
Adventure of the Seas (Southern Caribbean) - 5/9/09