How much gain with lower gears?

I went from 2.76's to 3.55's on a very mild 340 in a Demon and I dropped 6 tenths. However, it wasn't the same day, and it was a little cooler. At least 4.5-5 tenths were the gears.

However, I went from 4.30's down to 3.91's in a mild 360 in a Dart Sport and the E.T. was exactly the same.