On the eve of the launch of the Windows 8 Release Preview, a near-final look at Microsoft’s next-generation desktop OS, Apple CEO Tim Cook says that the software giant has it all wrong. Windows 8, he says, is a mistake, a “baggage”-laden product that “forces” together the PC systems of old with more modern tablet ideas that Apple invented.

Cook’s comments came Tuesday at an industry conference, a rare chance for one of Apple’s leaders to speak outside the comfortable confines of the company’s own events. He didn’t hold back.

“[With Windows 8, Microsoft] is pulling all of the leg weight of the PC market,” Mr. Cook said. “You wind up with something that’s very similar to what tablets were 10 years ago. The more you look at combining the tablet and the PC, the more the baggage from the past affects the product. If you force them together, the tablet and PC can’t be as good as they can be.”

Apple’s approach, of course, was to base its own tablet product, the iPad, on its smartphone product, the iPhone. Its PC product, the Mac, has been developed separately but has been taking on technologies and features from the iPad and iPhone over the past two revisions. But Cook says Apple will never ship a “hybrid” product like Windows 8 that combines everything in a single OS.

“In my view, the tablet and the PC are different,” he added. “You can do things with the tablet if you are not encumbered by the legacy of the PC. Products are about trade-offs, and you have to make tough decisions. You have to choose.” With Microsoft’s approach for Windows 8, he said, “the PC isn’t as good as it can be, nor is the tablet.”

And according to Cook, while Microsoft pioneered the Tablet PC over a decade ago, it was Apple that invented the “modern tablet,” with the iPad. “We didn’t invent the tablet market,” he said. “It was there. We invented the modern tablet.”

This isn’t the first time Cook has disparaged Microsoft’s approach with Windows 8. Last month, in a post-earnings conference call, he quipped, “You can converge a toaster and a refrigerator, but those things are not going to be pleasing to the user.” That said, Microsoft got the last laugh when its head of corporate communications Frank Shaw replied on Twitter with, “Must be a typo. [Windows 8] is not a toaster/fridge. It’s a toaster/oven. Those seem pretty popular. Just saying.”

But here’s a final snub from Cook, just in case you were going to give the guy a pass: He also referred to Windows Phone as Windows Mobile, a common technique for those wishing to passive-aggressively downplay Microsoft’s latest smartphone platform. Cute.