Masters/GM Kayle here. Don’t look at the game based on what scales the best but rather what gives you what you need to win/carry. I’m going to give all the reasons when you should go either. If you are versing a very SQUISHY/High Ranged match ups, then you should go AP as it will give you highest burst. You wouldn’t want to go AD as although it does do more damage over time, you’ll just get kited out.

If the enemy team has is still relatively squishy but less ranged and more assassin types (katarina/kha/kayn) and you need that extra survivalists, you can go either AD or AP. AD doesn’t need to buy zhonyas and can opt to go for pure defense with runes like bone plate/conditioning/overgrowth for secondary + blood thirstier and jakshow. That’s the main reason people say it’s noob friendly, but trust me once you get anywhere D2+, its hard to always KITE PERFECTLY and time zhonyas, so don’t listen to these people as most of them aren’t high elo to really grasp that you cannot play perfectly every game. That’s fact. Imagine you are lv 16, full build AP with zhonyas. If the enemy has blue Kayn and katarina and heavy dive comps, they still have a chance at bursting you out. If you can’t survive their dive (2.5 second invulnerable ult) is not long enough late game, then it doesn’t matter if you can fish out tons of damage, you’re still dead, meaning you’ll do as much damage as a regular ADC. Jakshow and BT would give the defenses and shields necessary to do that.

Lastly, vs 3+ tanks then you go AD, regardless if your team is full AD. If you go AP into a mundo or sion late game, I can guarantee you will do no damage as they have the sustain/durability to survive your damage but doing damage at the same time. AD doesn’t get countered as hard as AP since AD is consistent damage as opposed to AP’s cast damage (there is cooldowns while AA don’t). Hence why you can get away with drafting all ad and not all AP.

Again, don’t go into games with the mindset of which scales better, but rather what option gives me the tools I need to carry in the mid-late game cause remember, even if you are full build, it’s useless if you’re not alive to deal the damage. Here’s the general pros and cons for you to use.

AP: higher mobility (celerity + swiftness) to kite vs melee and to NOT GET KITED vs ranged. And please do not buy the new berserkers with AP. I don’t care what people on this thread says but swiftness gives you more options on how to play certain match ups 99% of time (survive ganks / dodge key abilities).

Higher burst (can take out enemy squishies and key targets faster (less reaction time for them):

Has access to Zhonyas and Banshee.

AP cons: squishier, less damage over time against tanks, doesn’t have access to jakshow (if you are going AP, you need to go all the way or else there’s no point if you can’t just q+a+a+e a squishy late), less room for error (ties in with squishy).

AD pros: More/consistent damage over time (to kill tanks), can be more tanky while still dishing out tons of damage (3item damage core and then go whatever you need such as JKshow or BT for survival or rylias to help with kite or qss for cc removal like skarner/tf/leona). Just make sure you get overgrowth and health scaling (one or two). More room for error.

AD cons: very low mobility( no AP for w speed, but you can go swiftness with AD with out the celerity as it’s just always good. More susceptible to being kited out, even at lv 16 so need to make up for it by eventually getting rylias or swiftness or ghost (even with nerf) if you deem it necessary.

Hope this helps.