This is a really simple question of preference, but when tagging:
For communities, are you more partial to !community or /c/community?
For usernames, do you like or /u/user more?
For me, I prefer the former (! and @) because it feels quicker to write them that way and it helps me create mental separation between the Beehaw/Lemmy way vs. the Reddit way. Also, when linking, I like the more instance-agnostic link styles [!community](/c/community@instance.com) or [@user](/u/user@instance.com), even though it takes a bit of effort to write.
I have little preference.
!and@are definitely faster, but having been a heavy Reddit user for more than a decade, the/c/and/u/signifiers are definitely closer to my pre-existing habits.