Unlike the 680 you can gang any combination of channels (they needn't be adjacent channel numbers like on the 680), adjusting trim for all using the lowest numbered channel in the group.
But the 680 makes it faster and easier to un-gang channels to modify the relative input balances between channels when necessary, re-ganging quickly again for global control, as no menu diving is required. Its also much faster to make and break multiple groups. 680 wins out in this regard for me as I never need non-sequential channels ganged, but I typically balance each channel against each other in a stereo pair, then gang channels in pairs to balance each pair against each other, then gang all channels for global control.
[Edit- Also, the with the F8, all channels in any ganged set are forced into having identical input trims. If trims are set differently prior to ganging, they are changed immediately upon ganging, with no on-screen indication of this unless drilling down to check trim level of each channel afterward. This is one of the main things I'd like Zoom to change via a firmware update. Forcing equal input trim is helpful if recording using an ambisonic microphone, but not necessary as the trims could be manually set to be equal prior to ganging.
Although DR680 only allows for one ganged set of channels, which must be adjacent to each other, it does allow for different input trims across the ganged channel set. That makes it far more useful to me. Lack of that capability on F8 makes its channel ganging useful t5o me only for individual pairs, not larger sets. Unfortunately]