There'd hardly be a difference, based on my experience with replacing 5600rpm drives with 7200rpm ones in several laptops.
Once a drive is spinning, it doesn't take much power to keep it that way.
A 7200rpm drive will do its job in less time, as well, potentially letting it sleep earlier in some applications.
But I really doubt you'd notice much difference. Speed and responsiveness might be another story, however. You will definitely notice that. (But the improvement from jamming in more RAM is even more noticeable.)
Note that the lower spin-rate drives have larger storage capacity. This is because larger tolerances must be used for track spacing in the higher-rpm drives. I'd rank the higher-rpm drives as slightly more robust physically, as a consequence.