Well, as with all of Bertini's Mahler performances - save the 8th, and possibly "DLvdE" - neither would be my number one first choice. Yet, they both comfortably fit into the characteristics of his entire cycle: very well played; very well recorded; straight forward, no nonsense conducting, etc. Bertini's M6 has very good cowbells that are probably less prominant than Chailly's. I don't remember the hammer strokes being overwhelming, but neither are they wimpy. It probably wouldn't become your top favorite, but neither will you be disappointed. In M3, that Killebrew lady will make you think of Harmon Killebrew (Minnesota Twins). She has a big and deep voice - she might be a true contralto. The third also has a very solid trombone solo. The beauty of Bertini's cycle is just the consistancy from start to finish, in terms of the three major elements I mentioned.
Barry