I guess that the thing here is that the banner post is big enough that people are going to hit the ‘x’ and not see it again. Whereas a titled link is something you might want to appear for a while (you might even time limit it).
I will see how this works out, maybe people will read and digest the banner out the gate but I have a rather more cynical view of how people operate such systems. Then again, would they click the link…