I think allot of this comes down to you sitting down, listening to some tapes and figuring out what you like.
I understand that this is a common statement for such requests, there are some issues with this:
> finding a single show (ideally of a music style that you will be recording the most) that has multiple recordings but only 1 piece of equipment changes from the other sources is next to impossible to find.
> if you can find the above, are all of the sources in the same config (x/y, ortf, din, etc) AND in the same location (vertical/horizontal plane)?
other than knowing various people that have all of the various pieces of equipment that you are looking at and can set up a true a/b test in a controlled environment, there is still WAY TOO much guesswork involved and it is a VERY subjective experiment.