User blog comment:Obyvvvatel/Magic resistance isn't effective./@comment-6061249-20130516210047

While people keep saying that it's not true, i find it incredibly true. Look at AD champions. You mostly need only Tabis + Thornmail = 3200 gold and you are loaded up with almost 200 armor at 18 plus bonus reduction. Just 3200 gold, 2 slots, remember about awesome damage reflection from Thormail. Try now with magic resistance. Two slots. Mercury + Spirit Visage. 3400 gold. What it brings? 75 magic resistance, total nearly 120 at 18. Also some health, cooldown reduction, healing effects and tenacity. That's all. This is likely half of stats that armor items can provide you with. 200 armor + reflection + 10% AA damage reduction means that you are nearly unkillable in 1v1 against AD champion and you're tough stuff in teamfights. 120 magic resistance plus small bonuses plus pretty nice tenacity. What is it? Definitely not that much. Still instagibbed in teamfights, maybe hard to kill in 1v1 vs AP. Tenacity is nice bonus, but it's worthless while you're instagibbed (and i don't mean 3 seconds combo placement as instagibbing).

Magic penetration is hard to get? Sorcerers + Liandry + runes + masteries + Void Staff = pretty enough. And you still get such stats as ability power = money isn't wasted. While armor penetration is a bit more effective, it's still nonsense. As long as you won't afford Cleaver + LW you won't feel bigger difference (35% from 200 is still 70 which leaves 130 plus runes and masteries = +/- 100, so it's still 50% defense, adding Cleaver stats mixed with the rest leaves something around 70 i think, while 35% + 15 + 15 + runes & masteries from 120 leaves +/- 35, LW + Cleaver = 5300 gold, also grants pretty much attack damage and a bit of other stats, Liandry + Void Staff = 5195 gold, i don't count Sorcerers because those are boots, but with them it'd raise to 6295 gold, making armor penetration still a bit cheaper, but in fact less effective).

Maybe i'm wrong, but i'm not going to change my mind as long as somebody won't bust the things that i've written.