Hexbins that aggregate all points in an area might be a better way to show the density of points than semi-transparent circles for each point in the data. This example draws a hexbin grid over the circles for a rough comparison. Each hexagon is shaded based on the number of points that fall in its area, with darker hexes containing more points.
Forked from Correlation Matrix IV and remixed with tiny hexbin plot by micahstubbs
Originally inspired by the Simple Correlation Matrix block from emeeks