Strategies to archive high frequent data in SQL Server
If performance is your only consideration if I were you I would consider partitioning your table(s) rather than just deleting the data.  Then you could look into either log shipping (if you want the whole database to be updated) or replication (if you only want a couple of tables copied).  As an alternative you could look into change data capture as a method of storing the changes you are making to the data.  You can then pull this information out to apply it to your other database.