Its up to you.
Atk speed will make you hit faster and (crucially) lowers the cooldowns of your skills
Crit rate will make you hit harder and will apply your crit damage much more often. High crit rate coupled with capped crit damage is a monster to deal with, but you wouldn't be happy with someone assaulting you with attack after attack that you cant keep track of either.
Highlighted crucial points of my post. hope it helps.
Edit: Personal opinion: I think its better to go for speed earlier in the game, then even it out with crit rate once your crit damage is up to scratch. With the attack speed you have already compiled you will be able to proc your crit rate faster than if you had poured into pure crit alone (Or at least, have more chances to proc it in a shorter space of time) Raise your crit damage as much as possible, this is where most of your damage will be coming from once you place points in crit.