Which is greater in RPM, 5400 or 7200?

7200 is the faster disk access. 5400 is pretty standard but if you can shell out for a faster RPM then it is very much worth it. Even better, go with an SSD.

There are issues with SSD's that most people are not aware of, such as the loss of data when the power is off for extended periods of time (recently reported information). A 7200 rpm drive will provide faster raw access speeds to data, but the overall speedup will depend upon whether you are accessing recently used data, or not. Most modern operating systems cache recently accessed disc data so that if you want to re-read that file, it will already be in memory so access is at RAM speeds - far faster than SSD's or getting it off of the spinning media once again.