Help me decide please. The 24-70Z (F4) or 24-70GM (F2.8)?

I am sure that this topic has been bandied about on this forum in numerous threads but I am still struggling with a decision. Is the 24-70GM really worth twice as much as the 24-70Z? There seems no doubt that the 24-70GM is getting rave reviews from those who own it. But does the 24-70Z really deserve the bad reputation that it seems to be getting on this forum? Does the smaller size and lighter weight of the 24-70Z makeup for the reported softness of the edges as compared to the much larger 24-70GM? Or does the edge to edge sharpness of the 24-70GM make its size much more tolerable? I understand the obvious light gathering benefits of the F2.8 vs the F4, but what are some of the other benefits of a faster lens that aren't as obvious to a non-professional like me? I know that there is no absolute right or wrong answer here, but I would like to hear the opinions of those who own or have owned one or both of these lenses. I do have the 24-70GM on pre-order at Amazon. I currently shoot with the A7RII.  Thanks in advance, Dean