Electric guitars usually have narrow necks. Most steel-string guitars' necks are somewhere in between. If you have thick fingers, a wider neck will make it easier for you to play. If you have small hands, a narrow neck is more comfortable. This is called action .
Low action makes a guitar easier to play.
This is something a lot of people overlook. Most steel-string acoustic guitars have what's called dreadnought style bodies. These are big guitars, and if you're a small person they can be quite uncomfortable to play. When you sit down with the guitar in a normal playing position, you should be able to reach the soundhole easily, without having to stretch. If it's even a little uncomfortable, it will affect your playing.