While the unlimited 9 hole is a Weekly tournament, the unlimited 18 hole is part of the Monthlies. Alas, it doesn't change much.
They give great practice opportunities on all courses by repetition, accompanied by good XPs (tournament rounds are honored by twice the regular numbers). Knowing that averages saturate quickly, you may play each round to the end, exercising the final holes.
To me, a journeyman who scarcely gained a top 70 position, the awards would be a good motivation. Play CCC for a month (Feb. 14) and try to get the next award!
For a round at ease, I choose any nine of STA and RSG.
RSG and BPB share the advantage of a low Par while less difficult than OLY.