If you run both at the same time, probably. Although having 2 AVs is kinda redundant most of the time. You usually will find one is doing all the work and the other is just wasting your time searching after-the-fact. And, of course, two different AV Co.s are gonna have different views on virus scanning and defs.
NAV Corp. Ed. is great, though. Plus I like Symmantec's support system, newsletters, and knowledge bases.