I don't think there's any comparison in the air between EY F, which is probably one of the best First Class products around, and BA J, which seems to be increasingly headed toward mediocrity.

After reading the thread about how food on BA is appalling and everything is dirty and stuck with duct tape, it'll be difficult not to be impressed by the Etihad product.

Your flights are on the A340-600, which are likely to have Suites, especially on the LHR and SYD routes.

The maintaining status question is of course one that I cannot answer for you, but there is no question of Etihad being on of those airlines on which BA J is equivalent to their F.

As for the miles, depends on whether you'd want to fly Etihad again. 40k on it's own isn't much (return to AUH in Y), but another flight and you'd be EY Gold, so build up the bank.

I couldn't disagree more with your statement. How top end BA is is entirely questionable, and the purported very good seats are miles ahead on EY F (wider flat beds, 1-2-1, if not Suites), not to mention only 8 seats in the cabin.