I've been running the fhf for about the past 6 years and have no plans on changing. I recently bought a newer model with the attachment webbing loops for a holster attachment. I only rifle hunt for elk & mule deer, so take that into consideration if you are a bow hunter primarily. I have never had an issue with the way the top flap opens, but this is a personal preference thing. I like the way the fhf closes / secures the lid down vs magnets, I am not a fan of using a magnet to close the top flap. The fhf rides up fairly high on my chest, which I prefer. There is no bounce in the harness once you have it on and adjusted properly. You mentioned 10X42s, so I would recommend the medium size. The medium is slightly wider and the pouch is taller. I have some SLC 10X42s that are 2004 models and the medium fits my binos perfectly. I have tried them in a small and it was a no go.
For what its worth, the fhf was the first harness that I tried, so I really haven't compared it to any others because it works for me and the quality of the workmanship is excellent.
Hope this helps