I'd say it's GT.
In spite of claiming to do intensive research, MatPat really stretches the fuck out of arguments most of the time to fit whatever clickbaity theory he's trying to pitch.
Not only that, but he will alwyas try to port in-game mechanics and lore elements to the real world and that shit just doesn't work, and sometimes ignore critical elements of a game's story or universe to bend the rules even further in his favor.
I would go as far as saying that his FNAF theories are probably the best one's hes made, only because he takes full consideration of in-game lore and isn't trying to twist fictional shit to fit it in the real world, which I think speaks volumes of the show. Though that is probably because FNAF takes place in what you would consider the real world anyway.
It doesn't help that Pat comes off as strangely passive-agressive whenever he's proven wrong, this is despite his titular show having "theory" as one of the words, a concept that allows for challenging and refutation (if anything, a theory actually encourages refutation).
The dealbreaker, however, is the fucking cancer-laden, deliberately misinformed and painfully ignorant Deadlock series. Instead of addressing real, legitimate criticisms and debate about a game's mechanics and design, they just spew retarded fanboy shit that Pat """""researches""""" from forum discussions and shitposts, then deliberately stays "deadlocked" so as to not anger his own fanboys.
The worst offender, and by far the worst video on that channel has to be the Dark Souls deadlock. Whereas the ASSFAGGOTS one was kinda meh and touched on a few points, the souls one was pure fucking trash. It's just nothing but MUH 2DIFFICULT GAEM IS NOT CASUL ENUFF SO IT'S SHIT PLS NERFE DIFFICULTY WE WANT THE SKYRIM AUDIENCE and my testicles started growing tumors instead of sperm when it is stated that the game is also shit for hiding the rusted iron ring, a ring that (according to these faggots) is absolutely critical and necessary to complete it.
They could've touched upon legitimate problems with the game's design (the capra demon and the entirety of lost izalith, for example) but they just had to serve the "the game is too hard for me" kool aid to their betacasual audience who can't play worth a damn.
That's why I think GT is worse, it's nothing but deliberate lies, deliberate misleading, and willful ignorance.
Yes, it was an autistic rant, I don't care.