Priority, projectile, quick kill moves > speed, weight, and ok aerials.
I dunno, when you compared Zelda with Ike I just really, really found that misleading. Even when you gave examples (running speed, gimpable recovery, kill options) those are completely unequal. Running speed is pretty much the same speed for almost all the characters except falcon+sonic. Recoveries aren't gimpable against Zelda, she just has a harder time sweetspotting (which any good Zelda can do with practice). Ike's recoveries are gimpable because his trajectory is so predictable. Not the same thing. And the kill moves that each character have is used completely differently. Ike uses his kill moves (upsmash, uptilt, ftilt, bair) as a form of punishment (player knows the guy is going to roll->upsmash). Zelda can easily spam her reliable kill move (dsmash, fsmash) with out too much worry of getting punished herself. The properties of their kill moves are completely different as well (one relies on range, the other on priority/lasting time).
It's not a match where either of them have a clear, distinct advantage, but overall Zelda seems to have a slight advantage because she seems to be slightly like a "jack-of-all-trades" character. Her aerial game, ground game and "camping" games aren't the best by far, but the fact that she has them and all of her movesets are solid (besides dair), she has more options in most cases.
And getting early kills with both characters require incredibly precise "techskill" (knee for falcon, bair/fair for Zelda) and the staple, solid kill moves (uptilt, upair, bair, dsmash, upsmash for falcon, bthrow, upair, uptilt, dsmash, fsmash, upsmash for Zelda) all depends pretty much on player skill. But overall, Zelda's moves ARE easier to land. That is undeniable.
The biggest problem with Falcon is not that he can't "combo" (although it would help a lot), the problem is that his air mobility was pretty much nerfed to oblivion which makes his aerials decent at best. If he could leap like half of Final D in an instant like he could in melee, he would be really, really good.
But the reality is, his aerial speed is slowed down to the point that its easy to see whats coming most of the time. It's either a bair, or an empty short hop. He can't do a effective running nair/fair/dair anymore.