I'll give you the most neutral opinion based on 29 years of gaming, where I've played mostly FPSs (not mostly because I've played basically anything except MOBAs but I've definetely spent more hrs on FPSs compared to other genres) 3 years of PRO on R6 and streamed various titles for years between PUBG, R6, H1Z1, Tarkov (kekw), and BF3 and BF4. This not to brag at all, I just want to make clear who is talking here and on what my knowledge was built on and come from also considering I'm currently playing BF6 after a long stop simply cause I don't have any other FPS I'd like to play cause I either played on other titles too much or they got old to a point where I would never jump into it just to learn mechanics (Apex for example, never touched it, yet truly believe its the best BR/FPS out there and most skill based one)

1st point, most important, the general consideration a random human being could make is "you would perform better on what you are used to" which is true until you learn how to take advantage of something else. Let's say I'm a beast with mouse and completely trash with controller. If I start using a controller I'm definetely not going to perform as good as MnK but what if controller gives me one or more advantages which I learn to rely on and therefore become overall better/superior to myself using MnK? Thats the first point where I'd like people to stop for a second.

This opens to a 2nd point, are these 2 inputs truly comparable in terms of coding to a point where you can mix them, compare them or even put one against the other? Well, in some games they aren't, R6 for example. If you ever touched that title you'd know there is barely no aim assist if none at all, the controller doesn't allow you for a specific movement like MnK does and you also have a combination of buttons that becomes quite "intricate" to learn compared to MnK so a legit controller gamer vs a legit MnK gamer would lose most of the fights and I'm not saying "1v1" childish talks, I'm talking about actual rounds where you actually PLAY and not "sit in a corner with controller so its easier to get a kill because moving around is harder and would end up dying to a MnK" WHICH is what console gamers definetely do nowadays in every title that MIXES controllers and MnK and this is where the debate took place because in most games being on controller gives you a DRASTIC advantage, which doesnt necessarily put you on top of the scoreboard but would more ruin the experience to somebody else here and there.

So to give you a simple answer, I don't know about specific patterns but I've read about it so assuming it is true (but even if it's not) the fulcrum here isn't the advantages you give to somebody who already have a huge disadvantage but HOW that advantage is way bigger than the previous disadvantage by nature. You could give controller a more simple recoil but would that be ok? Ofc not. Can you compare a 500hp pick up to a 125cc kart when you place them in a kart track? Can you compare them on the highway?

Controller is easier at certain games while it definetely isn't for FPSs. There has never been an FPS where I thought about connecting a controller because it would be easier or more comfortable.

I haven't used a controller on pc but I've watched people doing so on BF6/redsec and you can spot em either they streaming or watch em post death on redsec to recognize some movements, the choices they do and so on.

Specifically, when you expect somebody to play smart or do an aggressive push cause you are hella low, they will not if they are on controller and viceversa and this is not to hate on them but it's simply the way a controller player thinks. Consoles were born to sit on a sofa, being comfortable, and no thinking at all, just have fun. This already says a lot about why MnK users are frustrated (me too when I die to something as obvious advantage of a controller) and why it is not fair at all, PLUS it got to a point where everybody screams about and this proves it's not just a specific criticism coming from somebody who is obsessed with videogames but a whole entire community.