EK. None of the choices offer ideal situations - just don't expect it. Keep your expectations low and you won't be as discouraged. Abu Dhabi probably a better place to live than Dubai, but EK has all of the growth - 90+ A380s and 100 A350s with options. With your A340 background, you would be flying the A380 at EK in a few years. QR and EY are growing but people are getting assigned to the A320 fleets and they are not happy.
Again, don't expect the freedoms you enjoy in the UK. EK will do what they will do. Based on what I have read, EK seems like the best of the three choices (but certainly not close to ideal situation).