I've always considered Crit Rate better as I've never been able to stack Spell Speed to the point that it's notably different.
With the gear I plan on having I'll have:
Spell Speed - 493
Crit - 491
However, there's a thread out there that had:
Spell Speed - 564
Crit - 455
That gives them .07 faster cast speeds and GCD than me. It doesn't seem like that would make much of a difference at all. However, I just have a general mind-set that Spell Speed is useless so I was hoping someone else could inform me of any information they may have found about Spell Speeds usefulness. Everywhere I look has conflicting information.
I also don't know how effective 37 Crit is going to be.
It pretty much comes down to 37 Crit vs 71 Spell Speed.