Given that Mac is essentially BSD Unix, I personally don't see a pressing reason to try Linux (if you were using Windows, that would be a different story.
Mac OS X uses BSD Unix, which has a pedigree over 30 years old. Linux is a re-write of Unix that is about 17 years old. Linux looks and behaves almost exactly like Unix under the hood (there are still some small differences) and code that compiles on Linux will compile on BSD. The interfaces are different, but each have their own advantages.
If you wish to learn Unix/Linux, you can try to learn the command line and use other Unix based tools. OS X has a command line and it even has some of my favorite Unix/Linux utilities.
Download some of the programs available for both. I believe the GNU compiler is available for Mac. Mac may already have a C/C++ compiler available. If you are a beginning programmer, may I suggest starting with Python. The syntax is easy to use and it will give you a powerful tool to learn and write useful programs with.
You can maybe even pick up a book on Unix to learn about what's going on under the hood of your Mac. You'd be surprised how powerful the command line can be.
But I don't see any need to download Linux at this point. Both offer the same reliability and stability. Mac offers more commercial titles.