Personally stats I have of players I do not think is accurate enough as I for one play totally differently depending on what stage of the competition, and therefore I never am sure what stage I got the stats from for them, and how they were stacked at the time.
I think you are much better just gauging whether an opponent is loose or tight passive or aggressive by observing them in the current situation for a few orbits.
I always like to keep notes about interesting card plays, anything basically that I would likely not do often.
Eg, what sort of hands they 3bet with, or call 3bet with. Do they limp with AA etc.....do they chase draws and if so passively or aggressively, how they play their monster hands.
Just general stuff like that so that should I end up in a pot with them I am more aware of what they are capable of doing.