Though I do agree about 7x in general I would argue that 10x is more suitable for some applicabirding activities and other applications. Shorebirds are what immediately pops into my head here, assuming we aren't talking about also bringing a scope along.
For hawkwatching I use this combination...a high performing 7x bin to locate the bird and then, sometimes, a low power/wide angle eyepiece on the scope to ID. I tend to ID hawks based on flight behavior rather than plummage so this combination is extremely useful.
I am finding that a 10 power and 8 power combination works pretty well for me. Since my primary interest has been hawk watching, raptor birding, etc, etc, I blew some hard earned cash on a Zeiss 10x32 FL and love it. With a FOV of 360 ft @ 1000 yards, I don't often feel deprived when it comes to observing birds of prey. And the Zeiss FOV works well for almost all other species when I bird brushy areas that have some open spaces to work the edges.
What I am using the 8 power for is finding warblers, woodpeckers and other little birds in heavy brush along rivers and marshes. The wider FOV makes it quite a bit easier to pick up movement and get on to an LBJ when they appear. If I am out walking the 8 power works better with the shake (as I am out of shape).
For me as I grow as a birder, my preferences have changed and the profile of flying hawks is getting easier for me to identify. So the 8 and 10 combination is working right now. Regardless, I still feel a bit more confident with the extra increase in power.
I think if I was birding where there was more deciduous forest, a 7 power would make a lot more sense.
I can see that as I age, the day may come when an 8 power may be the better choice altogether. But at this point, the extra magnification is very hard to give up.
I'll see how I feel about all this in a year from now...and a bit more experience.
John