You should use one or the other.
USPS Is just giving two possible URLs to use.
I have found in some cases that using
ShippingAPI.dll
as the $WAGLOBAL_USPS_Server does not work and I've had to change to:
ShippingAPI.dll
Start of trying:
$WAGLOBAL_USPS_Server ="http://production.shippingapis.com/ShippingAPI.dll"
If that does not work, switch it to:
$WAGLOBAL_USPS_Server ="https://secure.shippingapis.com/ShippingAPI.dll"