NTT is the only one I have ever used. Freeze the hide, pack it in a styrofoam cooler, and send it UPS early in the week. 6-8 months later a package will arrive to you from UPS. Their prices are very reasonable. IIRC, a tubed bobcat was around $38, and a full WT hide was $32-34. You pay shipping both ways. That was several years ago, though.
If you do use NTT, don't expect good communication. They apparently stay VERY busy, and rarely answer the phone.