one has flat armor, flat mr, flat ad, and armor pen
the other has flat armor, flat mr, flat ad, and movespeed.
it depends who im against, but typically i prefer more damage than mobility, since you are constantly poking in lane anyways, and i want to win those poke wars in order to win the lane in order to carry my team
"You'll prob'ly win or lose, it doesn't matter what you do" - Dyrus LOL IGN: Octavyan
You get the AD quints for trades and last-hitting, if your support is exhausting/slowing their AD you shouldn't need the MS, and by mid game you'll have a Zeal/PD, so you're better off with AD. Movement Quints imo are more for bruisers like Jax who can really benefit from just a little more speed to get into gap-closing range