Shipping something from USA to Japan?

I have a friend in Japan that I am going to be shipping a game to next month, but I don't know what the safest/cheapest way to get it to her would be. Is anyone savvy in international shipping? Seems like USPS had decent rates, but I don't know the differences between services... For example:

Global Priority Mail - Variable Weight (Single) (4 - 6 Days) $13.75

Airmail Parcel Post (4 - 10 Days) - $21.60

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Global Priority seems quicker, and cheaper... so who would use Airmail Parcel Post? I'm just not seeing what the difference is. Maybe it's just best I go to the post office and ask them?

Sometimes the post office is retarded like that. For example, I just sent a 10 pound package (size was 16x16x10) to australia and Express shipping was only 3 bucks more than Airmail was. And since I needed DC/Signature/Insurance, it ended up being slighly cheaper. When it happens, just be happy and dont question


EDIT:

Global Priority is faster than Parcel. Basically, it's cheaper cause instead of going by weight or size, the postage is a flat fee.

Excellent, this will work out better than I expected then. Thanks so much for the info. The first place I checked was FedEx.com and damn near died when I saw the shipping charge was $50 (but their Super Bowl commercial worked, because the caveman was the first thing I thought of when I thought of international shipping XD).

Anyway, thanks again.