Use both Stranded and Solid.
Smallest size for typical stuff is #12 cu.
No #14 (unless control circuitry or Fire Alarm circuitry, then it's stranded).
Used Stranded and Solid for sizes #16, #18, #20 and #22 when work requiring these sizes comes along (Fixtures, lighting control COMBUS, etc.).
Will use Solid #10 cu only when available in stock (not wait 8 weeks!).
Will use Solid #8 cu only with a gun to my head!
Scott35