Flex Datagrid: MX vs Spark

Hi, I'm looking at upgrading an old App, build using MX Datagrid (version
4.5).

Critical functionality is the ability to 'freeze' 2 columns and 4 rows.

Am wondering if there are any advantages to replacing the MX Datagrid with
either the Spark Datagrid or the MX:Advanced Grid?

Thanks

David