 Solid Core or Stranded Wire? Heavy gauge solid core wire is generally preferred for high power applications, like the wiring in your walls. But for most, the biggest factor to consider is simple flexibility. Like say for breadboarding, solid's a natural choice. Stranded just doesn't get along with breadboard clips. While solid stays, you know, solid. And it'll retain the shape you bend it into, which is great for keeping the wire close to the board and nicely routed. It's great for anything that flexes frequently, distributing mechanical stress across many pieces as opposed to quickly stressing out solid core's single strand. No matter what kind you're using, consider adding strain relief to any flexing connection. And when you use a pair of wire strippers, make sure you reference the right side for your wire type. Or your strippers may turn into cutters.