The three tires you list are roughly equivalent, and Michelin's Defender series in Load Range E is essentially the Commercial T/A with a different tread, designed more for all-season use on lighter trucks and large SUVs. Bridgestone similarly has a tread pattern alternative to the Transforce H/T in their Dueler H/T line.
A step up in durabilty, with substantially heavier tire bodies (and in some cases steel rather than polyester in the body) will be Michelin XPS Rib, Bridgestone Duravis R250, and Goodyear's RSA tire lines. My last tire change I put on XPS Rib tires, knowing that I will not be using the RV on snow and ice.