AP Yi is hit-and-run, AD Yi is full engage. AP Yi Alpha Strikes, hits maybe one or two times (if he has Lich Bane) and backs off, heals, engages again. AD Yi has to stick to his target to deal damage. He's easier to counterpick, because he's kitable.

There's certain things you're not considering, and you disregard the importance of CC on Yi only. Yeah, CC works great on other champs too (Except Irelia, Fizz, Gangplank, Morgana's Black Shield, Sivir, Nocturne...Stop comparing him to other champs, he's not other champs) but CCing AP Yi is more difficult because of how you play him. AD Yi has to Alpha Strike to either engage you or dodge CC, while AP Yi doesn't stick around for the CC.

Also, AD yi is susceptible to snares and roots... which don't hurt ranged AD carries or AP yi nearly as much. Snared AD yi is GG.

What you're missing is the range of his poke. Alpha Strike has a range of 600, which is about the same range as many ranged champs' AA and many targeted abilities as well. From 600 range, Yi can hit champions beyond his initial target like the squishy ADC and APC.

Once he reappears next to the frontline champion (or even more annoyingly, next to a nearby minion that he Q'd), he walks away. What do you do, stun him and burst him down? He's already done his part: he just dealt like 3000 damage to your team with a lot of it hitting priority targets. Your ADC is now so low on health that they cannot safely participate in your team's counter-engage. If his team is positioned to start pounding on your team while you're trying to focus Yi, they probably come out ahead. To make matters worse, if the retributive stun and burst isn't enough, he pops meditate and all those cooldowns just went to waste. The teamfight is now 100% lost.

Compare this to AD Yi. He wants to go hit the ADC in the back row but he has to run all the way past the enemy front line and actually get into the ADC's autoattack range in order to close the gap the rest of the way with Alpha Strike. His gap closer is also slower than a true dash or flash ability (like Xin, Akali, Talon), so the team has a little bit more time to react.

AD Yi's damage potential and healing potential are both tied to how quickly he's able to get to his target and how easily he's able to stay on them despite CC and escapes. The more time he spends approaching his target, the less useful he is. This is not true for AP Yi. Against teams that position themselves poorly or are unable to react quickly to his aggression, AD Yi is strong. Against teams with good positioning that react quickly in a coordinated manner, AD Yi is weak.

What you guys don't get is that it depends on the situation. 1v3 SD to can burst down the enemy easy. But ap to would get melted once his q is on cooldown. 1v1 ad to is still better because of the damage he puts out. Ap to would be good to initiate team fights or clean up. You get it now?

You started the thread off by saying that it's not situational, that AD is just plain better.

My experience playing against Yi disagrees with you.

Theory is one thing, practice is another. Very rarely I run into a Yi that steamrolls, and it's usually because we're low on CC and not prioritizing our targets.

Fact is another. I very rarely see Yoricks but it doesn't mean Yorick is a bad champion, I've seen people dominate with him.

AD YI all day... AP yi is good when the team that you have a good aoe dmg burst. If not, the only ap atk u have is Q. W for heal which does no dmg so makes u a tank for the time of it being used until you get a heal reduction which then just makes you useless. AD yi has the most advantage as his passive is meant for ad, his ult is meant for ad, his E, and his q can act as a flash to closen to the enemy. He is also good late game unlike ap yi. I can only see ap yi good when he is fed or when enemy team are all weak and his q can refresh after a kill if your team do not take the kill which happens all the time. Way better ap champs out there just like ad champs.. but yi is still a very well ad champ plus he can split push awesome unlike ap yi.

There's been a lot of facts presented. AP Yi is currently better than AD Yi. AD Yi is seen more in newer player games, AP Yi more in higher wins games.

AP Yi is a midgame monster. You play him because just when teamfights start to happen, people won't have sufficient defense built yet to stop alpha strike from getting resets, which can easily give you a won teamfiight that snowball to victory.

AD Yi doesn't have the same midgame power - he has strong lategame scaling, but his vulnerability to CC makes him a niche pick there.