User blog comment:Drunk Bloke/Debate on Demacian Justice and Noxian Guillotine/@comment-109.144.209.138-20121025161107/@comment-62.226.26.240-20121026153309

think about the W again, it gives 20% bonusar/mr

that means that you don't have to build it up anymore (just a Quality of Life improv.) ans also that with ar/mr runes (which you will be most likely using) you are put at base defense values well around 90-100. That means you only have to get 20-30 ar/mr to have the same effect as the old W, every additional point makes the new W superior to the old one. it also decreases CC-effects on you by 30% friggen percent.

This way the former W is superior in earlygame, but less so later when teamfights errupt where you actually have to do something against the enemey adc.

Yes you don't have your awesome in-sprint E-cc-cancel anymore, but with mercury's you have about 50% cc-redux aswell as 30% bonus damage-redux for up to 6 seconds.