Along with Rattle's breathtaking rendition with BPO, the Sanderling is the only other Cooke version I'd keep on my shelf.
I have little to oppose against the Cooke edition. It's just that I am not as convinced about it as other are.
For me, either the Samale-Mazzuca (did I spell it right?) or the Carpenter version will do. Their completions sound 'fuller' and more authentically Mahlerian.
I'd recommend Sieghardt/APO/Exton for the former and Litton/DSO/Delos for the latter.
Going back to the Sanderling, yes, he added his own stuff at several spots even altering the original score. But Sanderling's reading strikes me as a near perfect realization of what's left over after Mahler's death. It's been some time since I visited the recording, so I can't say anything more than this.
John,