Having flown the King Air for a few years I would take the A320 job. In Europe it seems King Air flying is not that well recognised amongst recruiters and even EASA seems to work against you.
If you’re flying the King Air and wish to move on, it can take a while to make that move. If you’re flying an A320 there are many many more doors that are available for you to open.
Salary - King Air Captain £70,000.
Capital Air Ambulance are currently recruiting King Air Captains and pay £72,000.