Copypasting a comment I made on one of trance's videos:

My hands are not in the best shape right now for running games with KBM, but I still want to run this game using a controller. How much time do you think would be lost in PC any% by using a 360/Xbone controller vs. keyboard (even given that controller still has the quick turn button?)

Also thinking up controller strats for Normal difficulty

While I have yet to give this run a try (though I plan on it), I can't imagine it would lose a huge amount of time. Less optimal, but not horrible I think. As far as I can tell, the big pro to using K&M is greater ease in aiming and turning.

It would mostly be with your movement and looking at items (ie, the shadow puzzles) So it probably comes to just a couple minutes total of loss using the controller. Overall, nothing super big.

couple mins is actually a big deal in runs that are this short, hell in any speedrun 2 mins is a big deal lol. Being on topic, using a controller would lose u alittle chunk of time. But if ur not too worried about WR controller should be fine to speedrun with

Controller would lose time simply because KB/M is far more accurate than controller could ever be.

If the difference is a few minutes, that's also a pretty large deal.

KBM is far more accurate, I rely so much on quick turning just by muscle memory of spinning my mouse; thats something that could never be accomplished on a controller and in-game quick turning can never match due to the tiny pause times.

I think potentially you can up your sensitivity for controllers but I doubt even still it would come close to using a mouse; and if its a few minutes like Liv said, thats a massive difference

Ultimately, I think it depends on how far you want to go. If you want to be super competitive on PC, you need to use keyboard and mouse.

It's not an issue of competitiveness, Plywood, but of health. I used to be able to do twitch-heavy KBM stuff for hours at a time, but not anymore. A combination of tendinitis and nerve issues means that I'm more or less stuck with a traditional controller for any run that I do, and can't (or at the very least shouldn't) do long runs with KBM.