Comparison of SQL Server Compact 4 and SQL Server Express 2008 R2

Now that SQL Server Compact 4 has been released, some developers are curious about the differences between SQL Server Compact 4.0 and SQL Server Express 2008 R2. I have updated the comparison table from the excellent discussion of the differences between Compact 3.5 and Express 2005 here to reflect the changes in the newer versions of each product. FeatureSQL Server Compact 4.0SQL Server