I went to my local arcade today to do some research

. Played a time crisis 4, a BBH Pro and one I can't remember the name of (had big a green rifle in an open case on each side)
First the BBH Pro - CRT and lightgun as we know. Screen was on the way out and the aiming sucked. Also terrible at the edges of the screen.
Next the one I can't remember and the time crisis 4. Both had LCD screens fitted. The unnamed unit had 4 IR sensors top and 4 bottom. The TC4 had multiple sensors on all four sides (I think 10 or 12 in total). The unnamed was pretty accurate through the sights. The TC4 was spot on - really really accurate. Good to all corners of the screen as well as was the unnamed
So the IR won out big time. Much more accurate that the CRT. Blasphemy? OK the screen was not good so it wasn't up to full standard. But I know which screen I'd find easier to replace....
My aimtrak question- if arcade games use IR sensors all round the screen to work - how come AimTrak can use one bar at the top of the screen? Is it relying on better computing power to work out the position of the gun? Is this a compromise?