There are three main types of vanilla beans:
Tahitian vanilla has a light and fruity taste. The pods are short, fat, and have fewer seeds. They are more expensive than other types.
Bourbon beans have long slender pods with lots of seeds. To me they have a slightly alcoholic vanilla taste (not in a bad way).
Mexican beans are the same as the bourbon with a slightly spicyness added.
I personally like all three types. I can only buy one type for the restaurant so i picked the tahitian.