Unicode based programs ?

If you can choose, always select the Unicode version of a program.

As you say, being Unicode allows to understand text in non-English languages correctly no matter the system settings (ASCII is limited to English letters, numbers and the most common symbols only, and ANSI codepages are system-specific), so for it to work correctly with any possible text, Unicode builds are a must if the OS supports them.

Quick and dirty rule of thumb, if using a NT-based system, use Unicode if available (that is, for Windows NT, 2000, XP, 2003, 2008, Vista, 7, 8, 2012 and 10, use Unicode).

It's also important to note that it's not only a matter of using Unicode because you might use a non-English localized version, but any text the program handles is subject to bugs without full Unicode awareness. For example, a file manager must understand Unicode because you may have a file with a non-ASCII name, or more frequently, content that's not fully ASCII text (just try to open a chinese-named file with a non compliant program and you'll see what I mean)

If you're a programmer, then a basic understanding of Unicode is a must, as it's a fundamental topic in today systems, storage and data exchange. A good read about the topic is this one:
The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) - Joel on Software