You want to always pay for the stealth shipping, it's worth it.
If you don't pay for it, then they usually don't try to hide it that hard. Then it is a gamble. If the person at customs sees your seeds in the x-ray, they're gone. BUT, maybe it was a friday afternoon and the person was about to get off of his shift, and didn't give a shit and they went through. Or maybe that guy was looking for something bigger than a 3 pack of seeds, so doesn't care. You never know.
Pay the shipping and then if the person is a seed Nazi and destroys them, you keep getting packages until it goes through customs. The sender will try harder to hide them if they know that they have to send them again if they get seized.
Edit: Nazi might have been offensive to people that live in Nazi, so Hillary. If the person Hillary's them, (destroys them) they're gone. That may be offensive to Hillary, but who cares.