GPS L1/L2 position fixing incapability under heavy foliage is a thing of the past with the advent of GPS L5. This is according to GPS/GNSS sales people. With my very limited knowledge in telecommunication, I shall say without any degree of certainty that this is not true.
To my opinion, the only advantage of GNSS over GPS is the speed of position fixing. This is I guess due to greater number of navigation systems and channels supported. Greater number of satellites, channels, and frequencies prov