I actually really dislike those apple cutter things (the all in one push gizmos). No real reason I guess, just don't like them. Maybe its the cleaning, or that they don't cut around the core very well, or work super well on non-flat apples? Not sure, it could just be irrational dislike.
I was just going to say that I use a "dedicated" apple knife mostly because I don't do as good of a job cleaning my EDC after I cut stuff. I don't want to accidentally put some gunk from my EDC into an apple I'm about to eat. It might be a chicken and egg problem though. I know I don't need to worry about cleaning my EDC as much (more sterilizing actually), because I have the apple knife. I'm sure if I didn't have it, I'd do a better job cleaning...
And in all actuality, its just the food prep knife I keep in my bag at work. I just don't happen to do much food prep at work, and apples are the most common use for it, hence calling it my "apple" knife.
I eat them slice by slice (very thin slices), instead of cutting them into pieces all at once. And so some knives that actually cut the apple just fine, didn't work for the "keep apple slice on side of blade and lift to mouth" portion didn't work as well. The best example of that to me was the Case Peanut I used a few times. The super slim blade cut it great. But the chord of the knife is so narrow, that the apple pieces kept folding over the spine, making it more annoying to eat. The Opinel worked better for this, as its got a wider chord.