There are different types of international SIM cards, which one is best for me?

The most convenient option is a XXSIM card. It works everywhere, and allows you to save from 50-80% anywhere. When inserted in your phone, your phone no longer uses your number. It uses a foreign number. (Call forwarding is available, so that people who phone your North American number are automatically forwarded to your temporary foreign number.) Most world cards give North Americans a UK phone number that they use to avoid North American roaming charges.
A regional SIM card is a great option if you're traveling to multiple countries in the same region. For example, a European SIM card allows you to save 55-85% on "the continent."
Country specific cards allow you to save 60-90% and are the most cost effective option. For example, a France SIM card gives you a French number. While in France, you would probably be calling many French numbers. Obviously, calling France is less expensive with a French number than a UK number. People in France, would also be able to call you for less than if you are using a French SIM card instead of a world SIM card.
Frequent travelers have a XXSIm one or two regional cards, and a SIM card for specific countries. They carry them all in a convenient wallet size SIM card holder.