Is there a difference between mac and pc memory?

While there is no difference between "Mac memory" and "PC memory" there is a question of quality> Macs are more sensitive to poor quality memory and using modules that are not sold with a guarantee of Mac compatibility may cause kernal panics and general system instability.

As long as you buy from a place that guarantees Mac compatibity and has a lifetime warrantee, like Other World Computing in Woodstock, IL there would not be a problem.