Sql Server 2005 Editions Comparison
http://www.microsoft.com/Sqlserver/2005/en/us/compare-features.aspx
Sql Server 2008 Editions Comparison
http://www.microsoft.com/sqlserver/2008/en/us/editions.aspx
Compare Editions–Compact and Express for 2008
http://www.microsoft.com/sqlserver/2008/en/us/compare-specialized.aspx
Entity Framework can be used with Sql Server CE !
SQL Express v LocalDB v SQL Compact Edition
https://blogs.msdn.microsoft.com/jerrynixon/2012/02/26/sql-express-v-localdb-v-sql-compact-edition/