Flew TRK up for 5 years on the 737, although HDG was a pin selectable option which some operators (BA? ) used instead. Flown HDG up on the Airbus for years now and IMHO it's by the far the better choice. The top of the screen is where the nose is pointing which makes more sense to me, either seems to work but if I had a switch to select what I wanted it would stay in HDG the whole time.