I have read, but not experienced, that some acoustic guitars do not do well with heavier, i.e., medium, strings. In some cases the tension is too much for the neck and soundboard.
At least some manufactures specify medium or light, etc., for their guitars.
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins
-- Chet Atkins