Not to nitpick but your analysis overvalues the yield for settling on a food resource (+1
rather than 2).
Settle on grassland + work farmed rice = 7
(5 surplus)
Settle on rice + work farmed grassland = 6
(4 surplus)
The potential difference is only one
.
You see a 2
difference because you're comparing apples to oranges -- a plan where you grow a citizen to work the rice versus a plan where you don't grow that citizen.
Of course, that
is a relevant comparison, since that's precisely the "standard" quick expand does versus the accelerated plan MarigoldRan proposes.
Marigold's plan would be terrible if, rather than the greatly accelerated expansion he suggests, he instead proposed growing to size 3 and getting agriculture first -- I'm pretty sure the initial food boost would not overcome overall loss of food in that situation.
With gems our happy cap is 6, correct? With farmed rice we give ourselves considerable growth potential which will catch up and surpass the settled rice approach.
If your plan is to "grow to the happy cap then churn out settlers/workers", then yes, settling on the rice is a bad idea. But nobody is proposing doing that after settling on the rice.
Whether grow to happy cap then expand will surpass very rapid expansion is not so clear, I think. I was under the impression the general forum consensus these days is that expanding quickly is better than waiting for the happy cap. (although, several years ago, general opinion was the other way)
A much smaller point is that by settling on the rice you sacrifice the commerce bonus you would have received for it being riverside.
You sacrifice that commerce no matter what riverside tile you settle on. The only way settling on the rice will change how much commerce you bring in at the desired max size is if it means you decide to grow one size smaller, or you decide to work an extra non-riverside mine instead of a riverside farm or cottage.
Of course, do note that the rapid expansion plan gets a big commerce boost from getting the gems earlier along with picking up the gold sooner.