For myself the flying experience is most important, having every little button available is somewhat less important. I prefer to focus on the actual flying including tactics/startegy, both A-10C as well as the FC3 aircrafts are fine for this purpose (it's certainly not arcade style).
I use triple 50" screens (low-lag HD) in a otherwise dark cockpit cabin and the feeling of immersion is great, I have the front cockpit panel almost in full in view on my center screen so I can see all primary flight instruments without having to shift the view. I'm a retired airline pilot and I cannot imagine having to fly without those in view (I automatically scan those without moving my head, just quickly focussing my eyes there).
I prefer flying without having to navigate with a mouse, it distracts from realism. I guess this will change once I switch to the Oculus Rift, then shifting your viewpoint will become natural. Can't wait to fly the A-10C there :)
The thing that distracts me most from a realistic experience is the constant mechanical radio chatter, that's why I wish for being able to quickly adjust the radio volume in flight. I guess this feature would be easy to implement. Alternatively for FC3 the radio volume could be automatically adjusted depending on the background noise, but why make this complicated when assigning 2 keys in-game to the existing helmet audio option solves the problem.