I don't have a ton of experience with the Razer because I returned it so quickly and my memory might be fading. But here is what I remember:
Both headsets:
Work in both Windows and OS X. Headphones and mic work fine in both Win/OS X. In OS X they are stereo only. In Windows they are surround sound, but it's simulated. I don't think there is actual positional audio with either headset. So for example in a Windows game if someone shoots from behind, you don't really hear it from behind. The surround sound is more "immersive" than it is "positional".
Razer:
Audio kept cutting out in Windows VERY often. I run 64-bit and apparently that is a known, unfixable problem. The Razer is driverless, so there's no way to fix the problem with updated drivers. Microphone quality was poor, people heard lots of noise. There is a control box in middle of the cord that is awkward. Cords are a little awkward in general, but having a big box in middle of the cord makes it super awkward. About the only thing good was that it was comfortable. Oh, I guess the sound was good too, but that's hard to notice when it keeps failing.
Logitech:
Good sound, great software (in Windows), and good mic (people understand me). Cordless is pretty nice and the range is surprisingly long. I can walk around in adjacent rooms and listen to music. Controls were intuitive. You can easily get the mic out of the way by folding it up, which also automatically mutes it (way cool). In OS X there is no drivers or software, just plug it in and it works. Even all of the physical controls work in OS X. The headphones will turn off automatically with no use. Manually turning them off is a little bit unintuitive, but once you figure out how to do it, it is easy.
Basically the Logitech is really better in every way except comfort and sound quality where they are equals. I'm very happy with the Logitech in both Windows and OS X.