Nephron,
In small sizes, I've always been partial to sans-serif faces because I think they're the most readable. After I read your post, I did an experiment by typing a line of text, then duplicating it several times. I reduced it to 8 points, then applied 5 different type faces. By far, the best one was Arial, followed by Helvetica. But this is a matter of personal preference, and you should do some experimenting yourself.
-Dennis