USPS is the best.
I never lost anything when tracked and never lost any smaller cheaper items that aren't tracked. They make the post office look shite.
Dont use UPS as they are expensive and they always (for me anyway) get caught by customs and (some) even if they are marked by gift and low value. They are complete fookers.
I've had loads of cheap shite from Japan (games consoles stuff, gadgets etc, etc) and all marked gift and all get stung going through UPS. To get your money back then you have to go through a long drawn out reclaim procedure. It not worth the hassle.