I was asked for my thoughts on Fischer's Mahler 6, so here goes.
By and large, I feel that Fischer's "Resurrection" is clearly better than his M6. However, Fischer's M6 isn't poor by any means. The first three movements are rather quick and light weight - almost as though they are preludes to the finale. The finale, though, really is quite good. As I recall, the hammer blows aren't overwhelming, but are clearly sufficient. Timings are fairly similar to Abbado's recent Berlin remake on DG. Naturally, it's better recorded than the Abbado. In the first movement, I like how Fischer's "Alma theme" - the second subject of the exposition - simply jumps right out of the box. It's not in the least bit lethargic sounding, or overly languorous.