If it was on a normal board, fisher. If it was online, Bobby would be confused and run out of time by trying to move the pieces with his finger.
If Fischer and Magnus Could Somehow Play a 100 Game Match, Predict The Result.

Fischer started later in life, had less access to materials, less access to coaches, and played fewer tournaments, and in the tournaments he did play he played less strong players. He became a GM at the late age of 15 (although for his time it was a record).
It's not really a contest, and it's not a fair comparison either.

Fischer started later in life [...]
Although Magnus was first taught chess at age 5 while Bobby first learned chess at age 6, Magnus only took interest in chess (and therefore studied) later on, however, Fischer already began reading chess books that same year he learned. TBH I can't find information on when Magnus began to actually study.

Hmm, that's a good point.
I still think this it's not fair because, for example, Carlsen's father took a year (or was it two?) off work, took Carlsen out of school, and they toured around Europe playing in the strongest tournaments they could.
Compare to Fischer's father who... wasn't even in his life. Fischer live in (relative to Carlsen) poverty. There was no chessbase with a million games, he had books, and the best books weren't even written in a language he could read (he had to learn some Russian).
Fischer had genius and worked tremendously hard. Had he been born in 1990 who knows, but out-of-the-time-machine Fischer is not a very good player compared to modern elite players.

But think about Fischer's ability off book and out of Master game theory. There was still some originality in Fischer's day. Imagine Carlsen having to play in a world that Fischer was creating on the board.

Fischer wasn't some creative genius. He was known for being extremely well prepared in the opening and had a technician type style. His strength was endgames, his forte logical chess. When the position became a mess he was (relatively) weaker.

AI would analyze each player's entire corpus of games and then play the match simulating their strengths. We might see it soon!

AI would analyze each player's entire corpus of games and then play the match simulating their strengths. We might see it soon!
Accuracy of Magnus ia the highest.

AI would analyze each player's entire corpus of games and then play the match simulating their strengths. We might see it soon!
Accuracy of Magnus ia the highest.
Based on the Elo it predicts that a Kasparov - Karpov match would end 65% to 35%
In reality they played over 100 match games, and the difference was less than 1% in favor of Kasparov.
Engines are fun, but methodology is important, and simulations aren't reality.

Oh, this wasn't even something rigorous, it's chess.com CAPS.
That's just marketing BS. I thought you might be quoting some kind of actual work done on the topic

Hmm, that's a good point.
I still think this it's not fair because, for example, Carlsen's father took a year (or was it two?) off work, took Carlsen out of school, and they toured around Europe playing in the strongest tournaments they could.
Compare to Fischer's father who... wasn't even in his life. Fischer live in (relative to Carlsen) poverty. There was no chessbase with a million games, he had books, and the best books weren't even written in a language he could read (he had to learn some Russian).
Fischer had genius and worked tremendously hard. Had he been born in 1990 who knows, but out-of-the-time-machine Fischer is not a very good player compared to modern elite players.
For certain, Magnus would wipe the floor with him.

Oh, this wasn't even something rigorous, it's chess.com CAPS.
That's just marketing BS. I thought you might be quoting some kind of actual work done on the topic
This is perhaps the best comparison I've seen yet, note that it makes direct comparisons so no time machine here:
https://content.iospress.com/download/icga-journal/icg0012?id=icga-journal%2Ficg0012
Fish- 1w, Carl-2w, 5 draw.. then Bobby storms out claiming the internet was too loud.