We recently implemented a bubble chart for our system. The users loved it but wanted to see custom markers that would indicate "direction" of the data value. We couldn't see a way to put custom markers on the bubble chart (hence the term bubble I guess) so we looked at the scatter chart. This did everything we needed (custom marker, relative sizes, etc) but did not allow us to click on a marker that was behind another (like the bubble chart). We would like one or the other.