They can potentially be faster at outputting and refreshing vast amounts of information. It could also allow for smooth(er) scrolling. Human beings however are quite slow at reading this information, so I'm kinda doubtful this can be beneficial - the average person is unlikely to be able to comprehend it anyways. CPU usage could be lower but it needs to be tested.
At the same time such terminals are eating your VRAM which could be an issue for users who have little VRAM or VRAM stored in RAM (users with integrated graphics).
One way to measure performance is to generate or find a very large text file and measure the time and CPU time it takes to output it.
$ cat bigfile > /dev/null # cache it
$ time cat bigfile
Could be enough. I don't have terminals with HW acceleration, so I cannot test it.
I've just installed kitty.
That's for a 41MB file with over 700K lines:
$ wc -l test.txt
In both cases you barely can see or read anything on the screen.