Please realize, most general public use software is going to be available to either platform (Mac or PC) but when you are getting into technical software there are issues. These are probably not something everyone needs to think about but they are valid.
Some programming is easier to be dual platform than others. Much of the time it depends on the purpose of the program. Unfortunately they do NOT all run on an IMac just like a Windows progam won't run on Linux. I have programs that are Windows programs that won't run on Windows 7. (I've lied to my computer for years to get things to run on different platforms. Some things just will not translate despite the programmer's best efforts.) When in doubt, talk to the publisher (or programmer). They can tell you more about their product than any of us can.
Can't you imagine a perfect world where every program worked on every computer? All embroidery designs used the same formats, e-readers were on a standard format ... Technology has come a long way but has so far to go. By the time this all happens, these issues will all be moot points because these devices will be obsolete. Of course, I probably won't be around to see it.