Every airline is good as long as nothing goes wrong. It's about how they treat you when there is a problem and, based on my experience, Etihad is the worst of the lot.
Etihad is the best
Flew Gulf Air to Nepal a few years ago-planes ok but crew appalling. Wouldn't recommend them for CS but you get what you pay for. Wouldn't recommend Etihad either-they treat economy passengers with utter contempt. Had to take them to court a couple of years ago after they denied me boarding on totally illegitimate grounds. They contested the claim tooth and nail, spending tens of thousands in the process (I got sent the invoices as part of their scare tactics) all in a bid to deny my very modest claim. Once they lost, they didn't even show the decency to offer me an apology for their disgraceful behaviour-the barrister who represented them told me in private on conclusion of proceedings that Middle Eastern Airlines were well known for this sort of thing- I would advise staying away from all of them, except perhaps Emirates which has a marginally better reputation.
Gulf Air has new planes to London but older ones to India. A poorer cousin of Emirates or Qatar.