My main concerns are first the double crank of the 7.7 vs the triple of 7.9 as I have a 2012 7.5FX with double crank and it's a bear to ride when I shift to the larger gear/cassette. I wouldn't have this problem with the 7.9. Second, I have a bad back, so the weight is an issue. My 7.5 has disc breaks although excellent braking power, it ads weight to the bike of course. I think both the 7.7 and 7.9 will be light enough for me. Another thing are how these bikes look, I didn't physically see the 7.9 but the 7.7 is really really stunning.
Thank you all.