The c-stick isn't the best choice, at least not with Falcon. Falcon benefits alot from frame perfect aerials. I use both A and c-stick, but the best would obviously be to claw, so you can use one finger for c-stick and one finger for jump, allowing you to easily get the aerials out on the first possible frame.
Actually, I'd have to agree with him somewhat on this. I don't claw personally but I do understand what he's saying and why this might be a problematic situation without proper training.
The A button enables you to more quickly initiate an aerial that you would have to move your thumb to the C-stick in between. So for example on a fullhop double uair, you are able to more quickly get out the first uair, so as to have more time to get out the second. This not only enables you to more easily perform aerials and hit targets that are standing, but also enables you to choose when to go onto platforms.
More specifically...
On Fountain and Yoshi's, when the user initiates a fullhop (assuming they aren't doing the backflip animation triggered by pressing back as the hop is being performed) some aerials will cause the falcon to land on the middle platform. In the case of Dair, Nair, Uair, will all force him onto the platform if they are not initiated immediately after the hop is initiated.
If you use A for example, to do a uair, you can perform a second selected aerial more easily and not be forced onto the platform. This is performable with the C-stick, but most players will not be fast enough if not using a claw.
On Battlefield, Yoshis, Fountain, PK Stadium
The side platforms on these stages I believe to all be able to perform double uairs while rising and before landing on a platform from the mainstage. Essentially this allows the user to create a pseudo-aerial-wall if you will. So you can double uair (from the ground) in a fullhop and still land on the platform. This becomes useful in not only applying and retaining pressure, improving techskill and making noticable how quickly you are able to perform aerials before falcon lands from a fullhop.
So in other words, you can actually use the A button in the case of some aerials, to initiate them, thuogh it is more suggested that you use the C-stick if possible so that you can DI potential hits incoming while performing said aerials. If you can claw comfortably, you can perform all of these with your finger never leaving the space of the C-stick or X/Y. If it's already too much effort to switch, just perform certain aerials with the stick (within your control) but I'd caution using any aerial other than Uair with the stick, because it may force out strange problems. A uair, though you will be DI'ing up during any possible interruptions won't mess with DI's to the side, much (granted you aren't tilting heavily I guess). It won't cause you to fastfall or mess up a fastfall, the only potential problem is it can trigger a jump if you mash it up.
