Thy do market OSX as a more secure OS and given that safari is part that, you can infer that safari is just as safe.
You absolutely can infer that, since 99.9999% of malware out there is for Windows. OS X is very secure against Windows malware. You can download all the .exe files you want while using Safari on OS X. You'll be fine.
While it probably doesn't matter in the realm of things that apple typically is the first to fail in these hacker contests, the bottom line is they failed.
They failed every single year (if I recall correctly.) But it doesn't actually matter. Mac users are no more at risk now than the very first year of the competition.
Aside from Unix's security features - which we won't discuss since I'm inclined to let the Windows-majority's security-via-obscurity argument see some action, Apple's market-share - given their decision to own the Premium end and lock OS X to Apple hardware only, has given them a very comfortable position from which to "cheat" when it comes to security. Funny thing is, they can continue to do so without too much worry.
Notwithstanding Unix's security features, OS X simply is not a target, nor will it ever be, so long as Microsoft maintains its majority market share. Given that Apple deals only in the $1000+ end, Apple's current pace with security is perfectly fine. Nor, it seems, will they ever need to change it.
No matter what security argument you throw against OS X, Apple still emerges correct, and Mac users will continually emerge safe.
Even at the best of times Mac OS X market share has never really gone above what, 10%? 10.5% US? Nor does it need to. This is typical for the Premium end in any industry.
Apropos, I'm not really sure what the point is in MS gloating (or rather, their fans) about 90% share, when they're locked out of the Premium end. The people with money, the most well-heeled users aren't choosing Windows. That's not cool. When a company loses their Platinum-brand status to a competitor, it's nothing to brag about. Wal-Mart has cornered the market in plastic lawn chairs, but Ethan Allen sells the most desirable, beautifully-crafted gazebo and patio furniture.