Personally, I use Kelly more often for pencil-and-paper calculations and financial models than for making yes-or-no bets in the wild. For this purpose, far and away the most important form of Kelly to remember is “maximize expected log wealth”. In particular, this is the form which generalizes beyond 2-outcome bets—e.g. it can handle allocating investments across a whole portfolio. It’s also the form which most directly suggests how to derive the Kelly criterion, and therefore the situations in which it will/won’t apply.
Personally, I use Kelly more often for pencil-and-paper calculations and financial models than for making yes-or-no bets in the wild. For this purpose, far and away the most important form of Kelly to remember is “maximize expected log wealth”. In particular, this is the form which generalizes beyond 2-outcome bets—e.g. it can handle allocating investments across a whole portfolio. It’s also the form which most directly suggests how to derive the Kelly criterion, and therefore the situations in which it will/won’t apply.