My favorite probably was the Martin, followed by the Collings. Honestly, it was a toss up which was the Collings and the Martin and I really did not expect that the Collings had such a deep voice. But I was pretty sure that the Martin 16 series was not going to sound that deep (like number 4). Don't get me wrong, I have heard other Collings guitars that had the voice of God, but this one sounded almost too deep and dark. My guess is that I was hearing a little microphone proximity effect (boosted bass at a close micing distance). But the overtones from the Collings were very rich indeed.
The Taylor seemed the easiest for me to spot; nice balanced tone, clear trebles and not too dark. Very modern sounding acoustic.
The Yamaha was a pleasant surprise as it had much more tone than I would have expected from an "all lam" guitar. New strings really made it a "listen close" experience to pick it out of the bunch.
The Gibson really sounded like a Gibson to me. Honestly, I have not played too many Gibson acoustics (a few dozen maybe), but the ones I have played all had that sort of tone; rich, dark, velvety, slightly lacking in the sparkle of the trebles compared to the ideal "Martin" tone. I would not discount it as a bad sounding instrument by any stretch of the imagination. My guess is that it would sound great backing up a bright sounding voice (high tenor or soprano) and would also sound great behind a bright instrument (violin, flute, mandolin, piccolo). A set of 80/20s might bring out the clarity if that is what you are looking for, but I like the tone for what it is, great tone without sounding like a Martin!
I appreciate the string set offer, but I am loaded up at this time and the fun of the comparison was a gift in itself.
And to be clear, there was a fair amount of luck in that choosing. I should probably go play the lottery tonight.