My question would be why would you want to stay away from MS products? I realize that this opinion is a little different than what others posted, but I think that you're best served, and will be a better InfoSec professional, if you work with both. I would want to be in a heterogeneous environment so that I get to work with, and keep my knowledge current on, as many OSs as possible.

The problem with staying completely away from MS security is that a significant number, if not most, of the vulnerabilities seen on the Internet today are designed to exploit MS products. If you stay away from Windows entirely, you'll be at a disadvantage when it comes to intelligence gathering, incident response and management. Whereas a Windows/Unix admin might recognize a scan on X port as being a scan for a Microsoft-specific vulnerability and react accordingly, a purely Unix admin may be less quick to realize that, considering that they have little or no Windows experience.

Granted, there are other ways to stay up on threats, but I guess I don't see the point. WIthout sounding offensive, this sounds like nothing but elitism. I want to learn as much as I can about as many OSs as possible, and you can't do that by saying that you're only willing to work with one OS. I honestly believe that this could put you at a HUGE disadvantage, not just in the job market but in your ability to do your job.