Bert, there are no rules for this; except the ones you choose to make.
The major portion of raises is often based on somewhat arbitrary factors (length of service, education/licensure, cost of living). Nonetheless, I try to find a place to reward merit and quality of performance whenever I can. So when you have options (like the two you mention), I would take the opportunity to let their performance be the determining factor. If you are thrilled with their work, give them the extra dollars. If not...then don't.
