An boater who builds frames for a living told me once that he'd been pinned against a rock twice in an oar raft, once with a DRE frame, once with an NRS frame. The former was fine, the latter fell apart. These were probably different rocks at different flows so the story probably isn't entirely indicative of the respective strength of the frame, but I think about it every time the NRS junk mail comes and I look at their frames.
A friend pinned my Mini-Me on the Dolores and she bent WAY around the rock. The frame was fine. The frame was made by Ron at River Boat Works in Salida and is the same style as DRE. He's also the one that told me the story above, come to think of it. It was around $500 and had a low-back tractor seat and oar towers/locks