A virus is always a threat, no matter the OS. Which is why they make virus scanners for *nix and Windows based systems. They're not there to look pretty .
As for 'better company' Gateway shouldn't ever be acknowledged as a company, because all they sell is crap. Right now I think Dell is bringing back what it had before it went crappy, before they cut Michael Dell out of the CEO spot. Hes back now, they're doing a lot better and you can still get Windows XP on their machines. (Linux soon too!)
The plus to a MacBook (now that they're Intel based) is you can run Windows on it at as well. OSX, and Linux systems are becoming more 'used' by consumers, thus there is a lot more support for the systems. However the ability to install/run/operate Windows on the same machine makes it much more convent too. Macs are worth it, if you're willing to pay for it.
Another brand that is *okay* is "Acer".
Compaq machines (I prefer them to HP, though they're the same company) are more slick and less bulky looking than the HP machines.
Gateway is a *no* *no*.