Version 10.50.2500.0 (2008 R2 SP1) > (2008 R2 RTM) Version 10.50.1600.1 ???

I noticed that the version of SQL Server went down from SP1 to R2 RTM:
Microsoft® SQL Server® 2008 R2 SP1 - Express Edition Version: 10.50.2500.0 http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=26729 Microsoft SQL Server 2008 R2 RTM - Express with Management Tools Version: 10.50.1600.1 http://www.microsoft.com/download/en/details.aspx?id=23650 Are backups between these version in-compatible? Why is the R2 RTM version released with a lower version than the R2 SP1 version? What should people in production be using at the moment? 1> Stay with R2 SP1 until a R2 RTM SP1 release is available? 2> Upgrade to R2 RTM at next possible option? I would be very thankful ...