If you want a shot at command in the next 4 years: Qatar.
If you want a better roster: Qatar
If you want more money: Qatar
If you want better night clubs: Dubai
If you want more things to do back at base: Dubai
If you want a more social atmosphere: Dubai
I hope you're seeing the trend. Qatar is the better airline to work for and you'll move up to the left seat much faster. In fact you'll probably get a shot at command inside of 3 years. EK could take 6-10
Dubai is a better place to live.