A string changing kinda day here... I started with the X20 - it was time. My usual choice: Elixir Nanoweb PB Lights. I do like the feel of new strings.
Next up: the X10. The strings on it were still in decent shape, but I wanted to try the Light Mediums (heavier E-A-D) on it. The is a small difference in the acoustic sound (more bass)... but my finger said, "What are you trying to do to us??!!" Fingers can be over-dramatic like that.
I'll see how I feel about those heavier top strings after a few days with them.
Finally, the X7 got a fresh set of Elixirs. Sounds good, plays good. This is just a sweet little guitar. I think I went about 5 months on the previous strings, and they still sounded decent. Yes, the fresh ones sound even better. This was the guitar that was with us all summer in the motorhome, so it got a lot of play.
Perhaps digressing, but I sure do like my powered string winder. About an hour to change all three, plus some cleaning and polishing.