In this situation the bigger platters used in 200GB drives could well make a big difference compared to the smaller platters in the 80GB drives.
I would find out what size platters are in each drive.
This is why I chose to go for 2 x 250GB Hitachi Drives instead of 4 x 80GB Hitachis. The 250GB Hitachis have 125GB platters, the 80GB Hitachis only 40GB platters. Basically, read and wtites are much hÃÂgher with the 250GB drives as the platter density is much higher.
Just something else for you to think about