I'm not too well versed in the software world, so some other folk like dialup, Charon and squalor will have better opinions. I can give some general opinions though. The benefit of adding a sub category is that you can attach new property types to the category, but the downside is that you can't do permutations and combinations of multiple categories. Of course with property types you don't have a "top pick".
Personally I don't find the "Software Type" property that useful, and having discrete subcategories SEEMS to make more sense to me.