Similarities

• First and foremost, these are computers. They aren't religions. Indeed, as computers go, they're even running on the same basic hardware since the 2006 change over by Apple to Intel processors. Both are tools to get work done, both have keyboards, mice, windowing user interfaces and everything else needed to make a good computer experience. You can make an argument that both PCs and Macs do the same thing, but what matters is how they do it.
  
  

Operating Systems

• Macintoshes use OS-X, which is a prettied up version of BSD-Unix; this gives it a number of built in security features, such as proper segregation of administrator and user privileges; you will need to set an administrator password on a Macintosh. PCs generally use some flavor of Windows. Since Windows Vista, and more importantly, Windows 7, the Windows security model has gotten significantly better. Mac OS 10 is still more secure than Windows 7, but the gap is narrowing.
  
  

Hardware Pricing and Value

• One of the common gripes laid against Macs by PC users is that Mac users don't understand the value of commodity hardware, and pay a significant premium for the same hardware just to have an Apple logo on the case. There's a small element of truth to this: You are paying more for Apple's industrial design ethos when you buy a Macintosh, however that premium, once all the features are added up, isn't that much -- it's about $20-$50 more than you'd pay for an identically configured PC. The difference is that Apple traditionally has under a half a dozen models of Macintosh, while the PC industry has thousands of permutations at every price point.
  
  

Non-Exclusivity

• Two factors may render this debate moot (finally). The first is that Apple provides Parallels and BootCamp, allowing PC users to either dual boot their machine between MacOS X and Windows, or run Windows in a virtual environment. This makes it easier to switch between environments and use the software you like the best for any given task. The second is that with the rise of cloud computing and constantly connected mobile devices, what computer you launch a web browser from may become irrelevant in the near future -- and it's likelier to be a smartphone than a desktop.