I have no experience with the new G-Tech, but I did have one of the old ones (it was very plain-jane without as many features as the new one, and just a little bit bigger than a tic-tac box). The old unit was quite accurate (within .10 of the clocks at the strip) and it always read 2 mph faster than the strip on a 12.0@110 car. I will say this about the mph reading though it was consistant- in other words even though it read a little high it was always high-not all over the place. I will buy another one when I get finished building my current project.