That isn't very significant, and it doesn't sound like RDF was active for very long.  Were the R1 and R2 in sync?  Maybe the systems were in copy mode rather than full RDF/A mode?
We have a SRDF/A setup on a DMX-3 and its for a Sybase reporting server installed on a Solaris Box. Reports are performing very slow while SRDF/A is in use and they are performing quite well while the particular SRDF/A group is suspended. I could think this can be an issue with insufficient cache. But is there any other relation wrt performance difference?
SRDF/A & Read Performance on Symmetrix with Sybase