Agree with above, although some swear by a mortar and pestle. Naturally, you have more control over grind size with mortar and pestle, but they can tend to be more expensive than their electric competition. Can't say I've done side by side to be able to tell a difference in flavor.
Using an electric grinder is SO much easier for large amounts of spice. Usually for me it's when refilling my rub shaker.
I have a molcajete for when grinding up small amounts of spices, and an olivewood mortar and pestle that I use to make compound butter on occasion.