UK gives string diameters in thou.

Acoustics:
13s will always sound bigger and stiffer than anything lighter.   Lower the string tension too much nd the strings sound "floppy" (think: bouzouki).
Most of the sound in an acoustic comes from the vibration and twist of the top of the guitar. Reduce guage and tension: result - less sound, less tone. If you want thinner and boinglier, you may prefer the sound of a lighter guage.
14s and over - definitely for people who play tuned down a semitone or tone (step or half-step). Called "heavies" and hard to find.
13="medium" - and what people always used to play when girls were men and there were none of this nanny state (mutter, mutter). Even my late wife used to play them until the arthritis got her hands and the emphysema got her lungs so grabbing a chord and gripping became a non-option (no strength left). Some modern guitars will not handle them (Daion is one), so check first, but I am surprised to hear of an EKO folding.
12s="light". Use if 13 is not an option. Less vibration of the top, see?
11s="ultra light". Played by rock guitarists who think an acoustic might sound nice.
Lighter - those using non-standard tunings or pitches higher than EADGBE.


Electric: Guages make less difference because there is almost no body resonance and it's all about electricity.
7s, 8s. Played by youngsters whose hands have yet to harden, or people with impossible setups. Hard to keep in tune, and a determined bend can break them.
9s. Teles: the Fender scale is longer than the Gibson.
10s. Normal for a Gibson in spanish tuning EADGBE and concert pitch.
11s. Some "butch" players and metal players who play single drop D and have not yet thought of putting a custom bottom string on.
12s, 13s - usually those who play Spanish tuning down to D or even C. (Metal bands)
14s. Drop D tuning in the above settings, or even those who play in B and have not yet gone to a 7 string.


Curly hands? Bollocks.