User blog comment:Epegi/Hp/5 Vs, Lifesteal in the Early-Mid Game/@comment-4089515-20110929111545

Maybe on Riven this is the case, but for champions who rely almost exclusively on auto-attacks, such as Yi, Lifesteal is often better. Also, Lifesteal allows you to go in the jungle to get some extra farm. If you're REALLY low, HP/5 is better, but if you aren't at small amounts of health, maybe half, lifesteal is usually better. I haven't played Riven, so I can't judge, but I've tried multiple methods as Yi and lifesteal is the way to go. For Yi, that is.