Oh, you learn something new everyday . Missed that SSD.
Whats the difference between 5900 and 7200 if 5900 are capable of 7200 speeds?
"relatively" the same, the 7200 rpm drives will usually have lower average access/seek time and better minimum read/write speeds.
as long as you are comparing 2 modern drives, not like a 80GB 7200rpm drive to a 2TB 5900 rpm drive.