You messed up the quote tags here, but I'll break it down.
The range on Pikachu's up-tilt and d-tilt are greater than anything Kirby has short of f-smash. Pikachu's own f-smash is disjointed and out of a pivot outranges anything that Kirby can do on the ground. Pikachu's tilt game isn't only better; it's leaps and bounds better.
- Pikachu wins in the air
- Pikachu wins on the ground
- Kirby has to approach
I'm not seeing a 50:50.
Pikachu can do serious damage when he gets in on Kirby too. But there's a difference. Kirby can't really escape Pikachu's strings because of bad airspeed. Pikachu can just Quick Attack out of disadvantage. Pikachu is better in neutral and in disadvantage; they are tied in advantage. That isn't anything like a 50:50.
f-air and b-air go over a crouching Pikachu in most situations. You can do a grounded f-air, which will hit on its way down, but that can be punished by QA despite the autocancel because it takes a while to start up/finish the animation (and QA goes through it, which is hilarious).
Thunder is not predictable at all. The Thunder cloud
spike may be predictable, but when Pikachu jumps near you and uses Thunder, you can't differentiate between that and n-air or b-air. You can airdodge past him, but Peach has a harder time doing this due to her floatiness (thus increasing her predictability). Her best option is to n-air or f-air him away when he gets near, which is a fair approach (Pikachu's answer to this is up-air or airdodge->Thunder from slightly below her). It's not free by any means because Peach's up-b is pretty good, but it's also not free for Peach to recover.
By the way, Pikachu doesn't have to turn around to b-air you offstage. He can just b-air backwards while facing you, or if you're recovering from directly below the lip of the stage, he can drop down b-air.
Pikachu doesn't mind this at all, given that Quick Attack is a fast recovery and he only has half the stay-on time at the ledge as most characters.
This is almost impossible. Pikachu has a billion different angles on Quick Attack. How is it that you are claiming that most characters can avoid Pikachu's edgeguarding, but Pikachu can't just avoid something as simple as Peach's turnips? Let's turn the statement on it's head:
"Peach's turnips if you can actually predict their movement possibly, may also be easy to avoid. Quick Attack is at its best possible use here, if you can aim it with perfect timing, Peach can't do anything about Pikachu's attempt to get back on."
See what I did there? There are two sides to every story. Please be reasonably objective.
You're thinking of Quick Attack canceling, not Quick Attack. Quick Attack has been buffed since Brawl; it is way better in this game due to more hitstun.
Kirby's airspeed makes his edgeguarding way more predictable than Pikachu's. Seriously. You can see him coming from a mile away.
"what are most opponents gonna do when you use it on them as edge guards"
Not get hit, obviously. I have never been hit by Kirby's Stone, as any character. No character is forced to get hit by it, not even Villager or Ike. It's slow, and Kirby is slow. It's easy to avoid.