My guess is MS is using a simple memory speed test, and therefore, quantity of RAM will not improve the score. It may improve application performance - realized as speed - if you are running out of memory and your system must use the hard drive to store application data.
Quality of RAM is where you'll see improvement, though there are many other factors (many that cannot be changed short of replacing your motherboard) that will affect overall RAM performance. It's relatively easy to guage the benefit of more RAM. Get a resource gadget for your sidebar. If you are always against the limit (say 75%+), then more RAM will help. Either way, it can't hurt to have more than you need and it prepares you for the future.
Quality of RAM is where you'll see improvement, though there are many other factors (many that cannot be changed short of replacing your motherboard) that will affect overall RAM performance. It's relatively easy to guage the benefit of more RAM. Get a resource gadget for your sidebar. If you are always against the limit (say 75%+), then more RAM will help. Either way, it can't hurt to have more than you need and it prepares you for the future.