You can also make a shipping label directly from the Paypal payment at the same cost as Shippo.
I prefer that in any case, because my invoice, payment, and label are all on the same site. YMMV.
The SnapShip site gives the same pricing, it's CanadaPost, but you will be paying from a credit card and will have to enter the buyer's address manually.
All three are connected to your SfSB card number and have the same discounts.
PP also has a NetParcel service which I am deeply suspicious of.