I know. I know what people mean when they say "Mac" and "PC." But it's still wrong. "PC" is an abbreviation for "Personal Computer," which yes, really is as vague as it sounds. Your MacBook Pro is a personal computer, your iMac is a personal computer, your Dell Inspiron is a personal computer, your Chromebook is a personal computer, etc. They're all PCs. Please, for the love of all that is technically correct, stop pretending like Macs are something different and special from a PC.
If you're going to compare, say "Mac" and "Windows" or "Mac" and "Windows PC." "Mac" is a bit confusing, because it's the name of an operating system and also a product line of personal computers. If you're going to compare operating systems, say "Mac" and "Windows," seeing as they're both operating systems and now you're comparing software to software. Or better yet, say "OS X" and "Windows" because these days, the proper name is "OS X" and not "Mac OS X".
If you want to compare Macintosh (marketed as Mac) personal computers against Windows based personal computers, say "Mac" and (something like) "Windows PC." Without the "Windows," comparing Macs to PCs is like comparing apples to fruits... apples are fruits (think about it: if you were to say "Apples are way better than fruits," you'd sound like an idiot). Specifying "Windows" means now the comparison is specific and actually makes sense.