The absolute best stuff out there is the Samsung 28nm ram, but it's nearly impossible to find anymore.
I would go with the Corsair, since the Team Xtreem is already tightened on the timings.
That being said, you know that timings often make more of a difference than clock speed when it comes to ram latency, right? Which means that the Team Xtreem kit out of the box is going to be a fair bit faster than the Corsair.
Also, why are you only buying 4GB? I would strongly recommend a 2x4GB kit.