I've done better with double wall rims which seem to have much less tendency to twist -- one flange higher than the other, even when the rim is true -- When single wall rims are bent badly, twist becomes one more thing to manage. However, I find that lighter rims are much easier to work with because of their lower resistance to the spokes' forces.

As to what's worth saving, it depends on circumstances. I once had to save a rim folded nearly in half after a crash. It was when leading a tour, and there wasn't much choice. Straightened it by levering it in a grating until it was decent, then aligning. The rim cracked part way through, but survived 200 miles until we could get a replacement. At home, I would have simply written it off.