Hi Andy,
Would really appreciate if you can provide a brief comparison table or indeed tell me how does SCR differs from DAG in terms of its working ?
Regards
If you want to know how 2010 improved replication and site resiliency in general when compared to 2007 and why CCR/SCR etc are not used in 2010, there is plenty out there and is easy to find
Example:
http://technet.microsoft.com/en-us/library/dd335211(v=exchg.141).aspx
What problem are you trying to solve? Since Exchange 2007 is pretty long in the tooth, I would be looking at Exchange 2010 at a minimum and preferably Exchange 2013.