As far as the issue of German statistics go, Glantz is not 100% perfect with these. His tends to be sins of omission more often than blatant errors. He doesn't put in the level of archive effort like Zetterling does for German stats. Although to his credit.. in his more recent books (Red Storm, Mars, Stalingrad trilogy,etc.) he has used a great quantity of german sources and far more than the usual EF author uses for the soviet. Overall, his effort in this area is not that problematic.
In any event, cherry picking statistics without reading the words is not the main point of reading his books. He gives situational context and the soviet/german troop movements in higher level detail. That is the main value. Readers who studied the RKKA and Wehrmacht institutionally should have no problem visualizing the force structure while cracking open his books. German statistics can be found in other books like unit histories, Jentz panzertruppen I/II, order of battles, etc. in order to enhance the overall experience.
eg. Red Storm over the Balkans:
http://forum.axishistory.com/viewtopic. ... 4&start=60
http://forum.axishistory.com/viewtopic. ... 3&start=75
As far as Soviet source document/General Staff Studies go, their estimates of German forces and losses are wrong, so when Glantz reprints this for reference in appendix, for color, or in his document-dump books it shouldn't be a big deal. Their value is elsewhere and in the qualitative details.