I hate stranded!!!
It annoys me! You can't strip it well with Kleins, it sucks to terminate (small gauge stranded in a lug blows), and making a hook in stranded for a switch or plug, especially if you have to work hot, is evil! I despise making a light tail with stranded. It doesn’t twist up nicely at all. 2 or 3 #10 or #12 solid twist up real nice.
Len_B: I have never worked with stranded DX or MC (at least in the #10-#12 range). I assume you are not talking about an 8-2 MC, or something along those lines. Who do you get it from? Haven’t seen it here (about 8 hours down the coast).
GEO: Never heard if one or the other is required. I think some of it comes down to preference (not the NEC or AHJ), and some comes down to physics. Imagine a 4/0 solid piece of copper. That would suck! In a smaller size I don’t really think it matters much. A #12 THHN Stranded is no different in code than a #12 THHN solid (at least that I have found),