I have always been more comfortable with controllers. I am more than competent with a decent mouse/kb - I used to love playing fast-twitch competitive shooters. But that time is long gone and I struggle to see the utility. If I felt in some way that using a controller was holding me back, I would gladly switch, but I don't and a controller feels good, so why mess with it and spend the time re-acclimating to it when I don't have to? Sure, I still play single-player shooters where I might see some benefit, but I still succeed on the highest difficulties without it feeling like I'm fighting with my hands to make them do what I need them to with the controller, and my awareness of the fact that I am using my hands to manipulate a controller instead of moving a character on the screen drops off easily. That's never been the case with mouse/kb for me. It's never been as intuitive. I always just sort of know that I'm operating a mouse/kb setup. Even really, really good ones.
There's also the posture/ergonomics side of things. With mouse/kb I inevitably wind up hunching forward and not only getting too close to the screen, but putting undue strain on my body over longer sessions. I just tense-up little by little. It's almost as though my body wants always to be closer to my hands and what they're doing.
Have you ever gone to sleep maybe clutching your comforter or pillow, only to wake up finding your hand is so tight it's started to lose circulation? You didn't feel that happening, but little by little it was getting tighter until the reality hit you in a cataclysm of discomfort that made you unable to remain asleep. In this analogy, while I'm playing a game I am asleep, not realizing what my body is doing, until I 'wake-up' from the game and realize everything is sore. At this point I cannot play the game until that sensation is rectified.
With a controller, I tend to sit back in a more natural position. It's nice to have some freedom regarding where my arms are. I can easily find my way into a position where I can sit for hours and not struggle to get out of it when I'm done
I guess what I like with a controller is that it tends to make me calmer and more focused on the game. These days, I'm more interested in immersion than competitiveness. I want to have an experience, not master my fate in a game. I understand that for many, that's still mouse/kb. But for me, it's a good, comfortable controller. I think it's a matter of temperament and just... what you're used to. I grew up with controllers, starting with classic consoles in the very first years of my life. So they'll probably always be more comfortable and familiar for me. I know that people switch all of the time. I never did. And it's starting to feel like I'm reaching an age where my mind is sort of becoming crystalline... it's more apt to rest on the laurels of the skillsets it's amassed already. It's like it doesn't want me to learn new things unless I need to - and even then it takes more effort than it used to 10 years ago. Otherwise it'd rather improve what it already knows.
I will say, the exception would be any game with a lot of commands. RTS's, management games, certain RPG's... those are a nightmare to try to map a controller to. But they fundamentally aren't made for it.
