So if you hold down during a recovery animation or dashing, right before you get hit, it's no different from getting hit but not launched? There must be very little hitstun against grounded opponents, then.
Really? So the hitstun is still halved against crouching opponents, even if the attack is a spike or meteor? So is there no advantage to doing Marth Dair against cc'ers over just using Fair?
1. I think you misunderstood me. It sounds like you think the hitstun is changing, but hitstun and KB are only reduced when you do a true CC (your character is visibly crouching). If you hold down during lag, while dashing, or even after missing a tech, you take the same amount of stun/KB as you normally would, but you will ASDI downwards because that is the direction you are holding.
You get hit into the air, but on the same frame hitstun begins, ASDI is applied. Since KB and ASDI start on the same frame, the game can tell you were supposed to be airborne, but can also tell you ASDIed towards the ground close enough to land, so you "land" (missed tech animation) even though you never really left the ground. This same effect can happen even when you DO get a true CC, it will simply only happen at higher percents where your character gets knocked over despite the crouch's effect of reducing KB.
2. Some moves are more powerful than others, so they may have more hitstun, but CCing a move will cut the KB/stun in half whether it is strong or weak, spike or not. For what it's worth, I see this in practice a lot. When playing Peaches especially, they CC-dsmash my dairs with about the same frequency as my nairs. They both deal 12% unstaled, but idk if they deal the same amount of stun. I think it's more complicated because it's dependent on base KB and KB growth values which change what moves are stronger at varying percents.
Here is a chart Kadano made showing Marth's KO moves. You can see Dancing Blade (DB) 3 and 4 start out with relatively little KB, but their KB growth is higher so at higher percents, they deal better KB than moves that were stronger at lower percents. Thus, it is
possible most spikes are good vs. CCing, but if that is the case, it is because they all tend to be designed with a high BKB and has nothing to do with their trajectory. Someone would have to check the BKB of Falco's dair and compare it to his nair before determining if either was better, and at what percents. As far as Marth's fair vs. dair go, I think that is pretty similar to Falco's nair vs. dair. It feels like Marth's dair has stun, but that is probably a result of spikes having KB reduced by 20% with the same amount of stun. When you're talking about an opponent at 0%, it seems like he can reliably connect dair -> grab or fair -> grab on the same characters. This would suggest they have close or identical stun (at least at 0%).