I just got done mounting a Ronard 811 tripod yesterday. I used most of a 50' roll of stranded #10 from the ground clamp on the mast, down to the ground rod. Stranded wire tends to curl a lot so I had to use closely spaced supports (screw mounted tie-wraps in this application) to keep it looking neat. Solid wire holds its shape well after being bent or straightened. I used black insulation to match the cable run with it... but bare is fine. As I recall, Home Depot often charged slightly more for bare vs. insulated...
Bottom line: Bare or Insulated, Stranded or Solid, are all just as effective as grounding conductors. It's your choice.
Then we had a thunderstorm roll through...