Thanks for the tip about the USPS. However we want to offer a tracking number that actually tracks something, unlike the USPS. UPS gives a tracking number without having to ask specifically for it and without having to pay extra. I know they charge more. We have UPS pick up at our store everyday. That means I do not have to go anywhere or wait on the USPS to pick up from me.
None of the shippers will guarantee packages won't get knocked around so that factor is out of the picture. We do have our own packing boxes already that we can also use for transport to/from shows. The coasters fit perfectly in them. We have boxes that accommodate anywhere from 1-4 sets of coasters. We got them from Uline and good sturdy boxes.
From what I understand, the USPS has an additional fee for tracking. Also I understand that is actuality it does not track as well as the UPS tracking.