Solid versus Stranded Wire

[tom baker]

The big advantage of stranded over solid is later on when you have to make changes. Copper tends to self anneal and get harder as it ages. Old solid wire is very hard to work with in a box. Stranded is a bit bigger, but not enough to worry about.
We spec XHHW-2 for all runs underground...its harder to pull than stranded or solid, but lasts longer in conduit with water.