I definitely think notes are worth using, especially online. Memory is useful for general impressions, but after playing hundreds of
hands, it’s easy to mix players up or forget the details that actually matter.
The best notes, in my opinion, are not things like “bad player” or “fish.” Those labels are too vague and can make you play with assumptions. Good notes are specific and actionable:
“Calls 3-bets too wide with suited connectors”
“Overbets river only with strong value”
“Folds too much to flop c-bets”
“Shoves draws aggressively in PKOs”
“Slowplays monsters preflop”
I also like adding the situation where it happened, because context matters. A player who makes a strange call in a tournament with 5 big blinds is different from someone doing it 100BB deep.
Memory is still important for things like table dynamics and recent hands, but notes give you a long-term database of information. The key is not writing too many useless notes — after a while you just end up with a wall of text you never read.
The best players usually combine both: memory for the current flow of the table, and notes for patterns that repeat over time. A good note can save you a buy-in months later when you sit at the same table again.