It does matter, and you should always update the driver first, then the firmware.  New drivers can talk to old firmware, but old drivers cannot always talk (effectively) to newer firmware.  Occasionally, you may end up with a driver that cannot communicate with the newer firmware and the OS doesn't boot.  Another option - to save yourself an extra reboot, is to update them together.  Update the driver, skip the reboot when prompted, update the firmware, then reboot. You should also update the BIOS, then the ESM before updating the RAID controller as well.  BIOS requires a reboot, ESM doesn't, but the fans will speed up for around 10 minutes during the update.  
I have a PE 2950 III.  I installed OpenManage 6.2 today and the log shows that I need to update the PERC 6i controller firmware and driver. 2132 Mon May 10 13:22:23 2010 Storage Service The current driver version 2.14.00.64 (percsas) is older than the required driver version 2.23.00.64 (percsas) for a controller of model 0x1F0C: Controller 0 (PERC 6/i Integrated) 2131 Mon May 10 13:22:23 2010 Storage Service The current firmware version 6.0.2-0002 is older than the required firmware version 6.2.0-0012 for a controller of model 0x1F0C: Controller 0 (PERC 6/i Integrated)  Should I update the firmware first, then the driver?  Or does it even matter?
PERC 6i itegrated firmware and driver update