Power & Ease
Hi/Lo and KO, by most comparisons, are very close. But the ease of KO, IMHO, can not be overstated. Learning to count at your kitchen table is one thing, once in the casino with all the distractions, and trying to look like you're not counting, is another. After regular practice and a few trips to the casino, I was able to use KO almost effortlessly.
Matter of fact, KO has come so easy to me, in such a short period of time, I sometimes wish I had tried a more challenging system. But KO gets the money, gets you to the things beyond counting, like your act & cover, more quickly.