I've searched for a while, and I can't find an answer to my question, so maybe someone here can help me out.
With APC propellers, what's the difference between the 'electric' and the 'slow flyer' props if they are the same diameter and pitch?
Example: 10x7SF and 10x7E

Depends on what you're running it on... If it's a high torque motor, you'll need the one that ISNT the slow flyer prop. The slow flyer props are made light weight, the other you mentioned is more like a standard glow (although it IS lighter) prop. Make sure you get the correct one for your application, else the prop could disintegrate from stress.