30 spellspeed or 30 det on one piece of gear - no difference at all. But 30 spellspeed or det on 10 items is a big deal. I believe it`s all about the boss u are gonna kill atm.

Quote Originally Posted by Rainsford View Post
10 spell speed gives you exactly a .01 drop in cast speed
No it doesnt. The longer the cast - the more spellspeed affects it. Have just unequipped items ~30 spellspeed worth - lost .10 in the Raise cast and .03 in the Cure3 cast.

And it`s a good thing to remember that spellspeed affects not only the cast, but the cd as well.