Imho headtracking in combat flight sims is as useful as a joystick, ie. mandatory. It makes for a lot better experience and helps tremendously with situational awareness.
As for what kind of headtracking, I'd take FT over TIR at the moment. For me FT has done everything I've needed with a fraction of the pricetag and without much of a CPU hit. The majority of the time I'm seeing 1-3% on a single core, topping out at around 5%, and I'm only using a chepo webcam which isn't the most efficient solution. You can then spend the extra money on a new monitor for example
