One advantage we see with G+ over FP+ is the ability to have overlapping reservations. With FP+, you could not have overlapping time ranges. With G+, you can. On a recent trip, we actually stacked reservations for later in the day, and we were able to do 4 attractions in less than 2 hours. The 'modify' option really helps. With FP+ we often found down time waiting on the next reservation window. As with any of the changes Disney makes to their parks over the decades, there are pros and cons......