Solid core wire, on the other hand, is stiffer and is often used for permanent in-wall installations where flexibility isn’t a concern. For most users, stranded copper wire is the better option ...

I don't think it will matter much for a few feet of internal wiring, but since you make a case for it, please refer to the AWG Table below. This is for Solid Core Wire, Stranded wire is slightly less ...

I kinda thought that a solid core would be better since you wouldn't have to worry about internal breaks in the wires, but then I though about any kinks in a solid core wire might also degrade ...