After I finished recording the video I went back and set the compression in WME to 15 frames per second with key frames every 6 seconds and exported again. The final size this time was 12.7Mb versus the 23.8MB size for the QuickTime export. The QT export looks quite a bit better though as it has none of the blurring and gray artifacts you will see in the video below. You can watch my screencast on Live Sync to get an idea of the quality of the QT export.
UPDATE: I rescaled the video to make it a bit larger. I'm not used to using YouTube and in the future I will have to start using a fixed region for my captures and keep in in the widescreen aspect ratio that YouTube prefers. To make this bigger (and to show another feature of QT) I rescaled this video to a larger size and didn't maintain the aspect ratio. It is easier to see even if it does look a little odd. The original WME version is still up on youtube.
Also it turned out that the WME encoded version wouldn't play at all on screencast.com, so in the future I'm probably going to live with larger file sizes and forgo the pain of using WME at all.