That kind of depends... If you have plants, you would want a bulb that provides the wavelengths (colors) they they need to thrive.
Aesthetics is what I assume you mean when you say the obvious... With no other factors, I would stay away from blue if you have orange or red fish, something with a warmer color will enhance their colors more.
Don't limit yourself to what you find in the LFS either. Places like Wal*Mart and Home Depot have a nice selection. And they are usually a heck of a lot cheaper. Any bulb that is the same length will do fine.
Most of the time, the LFS doesn't have as much selection as it seems. Since they are catering to everybody, freshwater and saltwater alike, much of their selection will be inappropriate for each individual consumer.
[Hmmm... either I took a long time to type that, our you guys were really fast! LOL]