Thiel CS 3.6 vs 3.7

Replacing my model 3.6 speakers has come with a great deal of hesitation. I purchased them used from a dealer in 1993 after owning the model 2 2s. I have recently acquired a pair of 3.7s that are shipping as I write this. I understand that "beauty is in the ear of the beholder", but has anyone had both and had a preference? I ask because I do think collective wisdom is important and I do not want to be in the position of letting the "newer and improved" mentality creep into my judgment. What differences could I expect to hear? Context is Hegel Mohican to Audio Research Ref 3 to McCormack (SMc Audio) DNA 1 with almost all mods including Plitron transformer. Balanced throughout with AQ Columbia XLR and Kimber Monocle XL speaker cable. AQ Niagra 1000 conditioner and Shunyata Alpha HC power cables. Thanks in advance.