User blog comment:Emptylord/Sandbox/Custom Patch Notes/@comment-4068613-20140214033305/@comment-4068613-20140311111854

It has (almost) the same effect on your average DPS, but it's also instantly and obviously intuitive to people who have heard about what a "critical" is. Double your crit chance is much more easily comprehensible than "double the proportion of your AD added as damage to your attacks".

They aren't conceptually very different in terms of complexity, but one is much more intuitive to your average gamer.

Yasuo's passive also reduces the damage dealt/crit (10% normally and 25% for tempest), so you could either secret buff Yasuo, or transform his crit modifer to multiply his crit damage by 1.9 (1.75 for Steel Tempest), which is less straightforward than "doubled crit chance".