Board Thread:League of Legends discussion/@comment-25866619-20141214020929/@comment-1330314-20141214032835

is the best MR item on Irelia by far simply because she has so much natural sustain: +2.6/5.2 extra HP doesn't sound like much, but that's the extra amount you heal per hit, which adds up to a lot over time. It can also easily heal her for 300+ more health every time she uses her ultimate, which is massive, and gives her a significantly larger amount of regen. Even if you're up against a physical damage champion, Spirit Visage gives you massive sticking power in lane, a ton of in-combat healing, and extremely quick recovery.