The 9.93 is, in my opinion, the best value chain one can buy (even at RRP). KMC's quality is in no doubt – they manufacture the vast majority of the world's chains, including all sub-XT-level Shimano chains – and their 'high-end' offerings are easily as good as the XT/XTR in terms of durability. I also prefer the shifting from the KMC x-plate design than the Shimano bulge.
I run XTR because I get them on the cheap, but when I've needed a chain at short notice it's always the 9.93 I go for. For what my opinion is worth, I'd never hesitate to recommend the KMC.