I don't want to sound like a Freedom Mobile ad, but another thing I really like is that I can turn off overseas roaming at the carrier level, in my account online. That way it is 100% off, even if I don't do anything with my phone or SIM. Which is good, because it would drain my pre-paid balance in seconds, haha. Not sure if other carriers offer similar options.
Also, as far as I understand, no pre-paid plan, Canada or European will work with celluar-at-sea. It might connect, but there will be no service. Only works with post-paid account that can be billed.