Ignoring Jet and Turkish Airlines ( apparently both are crap as well ), to summarize,
If you look for the following desirables and give points for top 3 per category :
-Cheap return Fare
-More miles to your miles account from your family members' journeys
-Gives more miles for a LHR > < DAC return journey
-Lower cash amount for taxes when getting a Free flight from miles redemption
-Less miles required to get a Free flight
( Emirates - 12 flights before a free flight, Saudia - 10, Jet - 8, Qatar - 6.5, Etihad - 6, Gulf - 3 )
,
Then the best airlines to take from LHR > < DAC are
1. Gulf Air
2. Etihad Airways
3. Qatar Airways
Hope this was of help to someone. Good night!