Gearing can be a pretty finicky thing - with a significantly shorter final drive like a 4.77 you will accelerate through a given gear noticeably quicker. However, the speed (MPH) you reach by your shift point will also be lower. The shorter final drive is can be beneficial because you spend less time in the gutless, lower RPM range. It's important to remember though, that you will also reach the limit of the selected gear at a lower speed. This can lead to more shifting to reach a given speed than it would take with a longer final drive.

Example:
Stock AP1: 40 MPH = roughly 5500 RPM in second gear
AP1 w/ 4.77 final drive: 40 MPH = roughly 6300 RPM in second gear

In this example, the car with the 4.77 final drive will accelerate faster from 40 MPH, because the RPM is higher, so it is generating more power. However, there are limits to these benefits. The car with the 4.77 will have to shift sooner (because it is starting from a higher RPM and will reach it at a lower MPH).

Gearing can be hugely beneficial in some cases, and a massive detriment in others. Shortening the final drive some (4.3, 4.44, 4.56) seems to yield the best all-around ratios for performance-oriented driving.