Well after reading through all of these great reasons, I suppose I should chime in with mine...
My favorite guitar to play is my Guild D-50, which I have owned for 30 years now (wow - how time flies!). Last January I bought an Epi Masterbilt AJ500 and that has gotten a lot of play time, mainly because it didn't come with a case (I bought a gig bag) and it stays out on a stand. My Guild stays protected nicely in it's case. For a good long time I was keeping both of them out and randomly playing one or the other. Life was pretty simple - then I added the Taylor 814ce and complicated everything

. I have been playing the Taylor a lot because it's new, but I do find myself A-B-ing the same songs on all three guitars - mostly between the Taylor and the Guild. The Guild has such a great big, rich sound, especially with new strings. The Taylor has a totally different sound and is very comfortable to play because being a GA it is not as big as the Guild, a dread. The Epi is also a dread and now I have it tuned to Open D - which I have yet to figure out (but am eager to learn). I also have the Epi strung with medium gauge strings and the others with Lights, but that doesn't really play into the decision on which to play.
When I play with friends, I just pick the one I want to show off - it's usually either the Guild or Taylor.
So right now, my order of play is Taylor - Guild - Epi. I like the idea of a planned rotation - playing one or the other for a week or month at a time. But I also like to switch between them as much as possible because I don't want to get too used to playing one over another as they all do play differently.
I think that after the newness of the Taylor wears off, it will be interesting to see which is my first choice - I'm pretty sure it will be my Guild. I love that guitar.
Great feedback here. It's been really interesting to read and I have learned from it.
Happy New Year!
Jim