But the important part is that there's a difference in feel and theme that's not really measurable and identifiable in direct comparison.
The subtle difference is far more important than trying to identify the tiny details that don't really matter. And in that sense, this game (while fun and interesting) misses the point.
It's like art: you develop more sophisticated tastes as you're exposed to better things. It's hard to say this without sounding snobbish, but if all you've seen is Arial, you'll find Arial familiar and comfortable. But the more time you spend looking at good typography, the more Arial will start to hurt your eyes.
Does this feel different? I can see the slanted Arial terminations but I don't "feel" the different mood.
In the wine world, it is possible to isolate this effect using blind taste tests. In the font world, there seems to be no robust way to show a font expert Helvetica without letting them recognize that it's Helvetica.