My wife and I are in the design process of a card game.
CodeQuartets (Codename) lets you play "Top Trumps / Ace Trumps" ("Supertrumpf" in german) and of course standard quartets.
If you´re not familar with these games, you can take a look here:

http://en.wikipedia.org/wiki/Ace_Trumps

However, CodeQuartets is not about cars, aircrafts or boats.
It´s about programming languages.

Currently every card has a set of data. To give you an example, here is the data set of C#:

class C# : C

class C# : C
{
private int yearOfBirth = 2001;
//
private int keywords = 76;
//
private float platforms = ;
//
private int helloWorldCount = 93;
//
private int rank = 7;
}

The rank is based on data from http://lang-index.sourceforge.net/

As it turns out, a lot of languages are theoretically available on every platform, so "float platforms" becomes infinite. This is bad for a balanced top trumps game, we need data which differs for nearly every language. On top of that the property must be suited for research.

So here comes my question:

Do you have any suggestions for some more properties?

Edit
To give you a small teaser, here is a very early, work-in-progress design of a card: