Yes there are, first at all if you didn't read (Very probably) NWPlayer123 said that is better not updating beyond 5.3.2 (Go to the first page and you will see the Twitter message), we don't know exactly why, but if he said that is because he has a good reason, maybe more vulnerabilities for one special hack like IOSU.
Now I remember, in some cases it was even recommended to stay in 5.2.0 MAX, why? because it was easier to exploit for IOSU:
https://twitter.com/naehrwert/status/655782468688199680
Now, there is another difference, the kernel exploit that 5.5.1 uses has another codehandler,
https://gbatemp.net/threads/splatoon-modding-hub.425670/
View attachment 51648
You can clearly read "This may or may not work on 5.5.0/5.5.1 since the codehandler may not function on 5.5.0/5.5.1"
But I agree the part some 5.5.1 user can give a opinion about this, even when we know the differences (Just I'm curious about the SplatoonHax part in 5.5.1)
EDIT: There is the Userland exploit difference, but that was obvious