Professional certifications .vs. academic degree

I currently work in the broad IT field and do a lot of things, ranging from systems administration to design and security implementation, I currently hold the MCSE 2003 cert. I am planning to specialise in the field of information security. Should I go for professional certs such as CISSP etc. or a masters degree in InfoSec? would doing both be a definite advantage? what is the trend that employers seek?