FFR
No matter what anyone says to you about Abu Dhabi, Dubai, Qatar etc they are still governed under the same law. Yes, Dubai you can pick up a beer in most places, but you'll still be banged up for kissing someone on the lips in public.
Financially, you will be far better off in Qatar as your digs will be paid for, including all bills (trust me, you'll die seeing what some people are paying to run their air conditioning, water etc out in this part of the world). Lets not go into too much detail. However, (maybe to be proven wrong in the next few months) rumour has it quite a substantial pay rise (10-20%) on the way. This should take the average FO pay well into 5k without any worry for bills etc.
Flying wise I believe Qatar wins hands down. Firstly, if you've been offered wide body experience, Id jump at the chance. The 330 really is the beach fleet here! Also, I see you're from the UK. I believe the 777 will start eating into most of the UK routes (as it is now) but you're open to a few nights back home. Your flight allowances will be pretty good also. The 320 fleet in Etihad only has a small handful of decent destinations.
I would say that Etihad, based in Abu D/ Dubai area will give you more freedom in terms of having a beer.
Money and Flying - Qatar Lifestyle/Partying - Etihad