Using the wrong compiler, you may wind up with an extension that appears to work, and you may never have a problem with it if conditions are just right.  This article[1] looks like a pretty good explanation of why you don't want to do it, though (note: I've only skimmed the article).

If you really want to shoot yourself in the foot, you can try running vcvarsall.bat yourself, then make sure MSsdk is set (distutils doesn't care what it's set to, just that it's set), and set DISTUTILS_USE_SDK (again, doesn't matter to what).

Also, note that this problem should be a thing of the past with Python 3.5+ and VS2015+.

[1] http://siomsystems.com/mixing-visual-studio-versions/