The problem with the Barshai version - and this is only an opinion! - is that Barshai has loaded the score up with lots of exotic instrumentation and excess filigree, but without addressing what I feel to be the major issues about the work, in general. To me, he has focused on the minutiae of the trees without looking at the overall forest. Some feel that Carpenter has done too much free composing in the course of his M10 project, but his version simply feels and sounds more completed than most of the others. Granted, Carpenter goes too far in bringing late Mahler into the more overtly expressionistic sound-world of Alban Berg's "Three Pieces" and "Wozzeck". But it's believable as a finished Mahler/Carpenter work.
Samale/Mazzuca are also more overtly expressionistic, but without sounding so much like Berg. This is particularly true in the latter half of the second scherzo, where Mahler's sudden outbursts just explode with terror. S/M also have the strongest ending to the first scherzo - a major weakness of that movement in general - and the best ideas regarding the last 10 minutes or so of the finale. Those are both major issues about the work as it stands now. Again, these are just opinions.