Roy-Andrè, you are right that the number of GBs alone do not determine the quality of the virtual instrument. However, all other things being equal it does. There are a number of variables which determine the size of the instrument, release samples, no looping, number of velocity layers, incorporating different characteristics via keyswitching (breath, key cliks, growls, bends, etc.) and so on. In other words one might refer to these as super SAVs. In the sampling world these instruments have been around for a number of years.

....but you are right that you can make very beautiful noises with relatively small byte size instruments. These are all great choices for musicians.