I think Apple should stay quiet until they have fixed the mysterious data wiping 'feature' of OS X SL!
As others have said, Apple has a different market to Microsoft. I don't even know why they are classed as competitors as such because Microsoft is primarily a software company and in fact gains from Apples success due to the fact that both OS X and Windows can run on the same machine.
I don't think that the virus and particularly the insecurity gameplan is going to work against Windows 7. Lets face it, no matter which way anyone tries to swing it W7 is a nice OS. Not as nice to use overall as OS X, and visually not as good (right click your mouse in W7 and you see the old grey W98 style box!), but there is no denying that it is a good OS. And I only used it in public Beta form, so the final release is only going to be better. But security is probably about the same on both OS's. The main issue with Windows is the number of malware programs in existence and the way that the general public is generally ignorant and continues to visit dodgy porn sites etc. Although maybe that would be a good line for Apple "Unlike Windows, with OS X Snow Leopard you can watch porn all day long without any risk of malware." There must be a huge market for porn, so maybe Apple can tap into those users
I think that Apple should concentrate on extolling the virtues of the really cool software that is available on the Mac and the seamless way it all integrates. Forget viruses etc, why not mention the way that Windows seriously clogs up over time and spreads DLL files everywhere. The fact that you can't just drag applications to the trash can to get rid of them. Or the fact that inexperienced computer users simply get on with OS X better than Windows mainly because it doesn't suffer from the aforementioned crap.
The big problem with Windows is that they have certainly made the user interface and overall experience better. But Microsoft still hasn't really touched the basic foundations of how Windows functions. If they had then they would have solved things like the need to install applications and the way that such process spread files everywhere. They would have completely ditched things like the highly problematic registry.
The problem is that they can't because it would take a monumental shift to do it and the same kind of confidence that it took Apple to break with the past and release OS X. In doing so MS would suffer from major incompatibility issues, the likes of which the computer world probably hasn't seen before. It would take years before such an OS gained true traction, and in all that time, just like Apple they would need some form of legacy support.
Although having said that MS might be indicating that way. After all W7 has an XP emulation mode.
