Learn Hi-Lo if you can divide by decks remaining without slowing down; learn KO if you can't. The two systems are almost equally accurate, and they differ in just one card and one step: KO counts 7s as +1 and skips the true count.
You want the most widely taught system, with the most books, drills and index plays
You plan to use strategy deviations, which need the true count to stay accurate at every depth
You may move on to a Level 2 system later, since they all use a true count too
Choose KO if
The true count conversion is where you make mistakes or fall behind
You mainly want to vary your bets and will play plain basic strategy
You play fast shoe games where every bit of mental effort counts
Our recommendation
Start with Hi-Lo. Practise the true count with the calculator until it's automatic. If after a few weeks the division still breaks your count, switch to KO: only the 7 and the starting count change.
KO is easier at the table because you never divide by decks remaining. Counting the cards themselves is equally easy in both.
Which makes more money, Hi-Lo or KO?
Played correctly, they are very close. KO's betting correlation is 0.98 and Hi-Lo's is 0.97. The bigger difference is how many mistakes you make, so pick the one you can keep accurately.
Can I switch from KO to Hi-Lo later?
Yes. Only the 7 changes from +1 to 0, and you start at 0 instead of below zero. You then add the true count conversion.
Practice on Android
Try Both in One App
Counting Edge includes Hi-Lo, KO and five more systems. Switch between them in a tap and practise each with live counts, bet sizing and timed drills. Free and open source.