One factor to keep in mind is the typical ground surface the rocket will come down on. If you are pretty certain to be landing on grass, you can go with a faster descent rate (and enjoy the smaller packing size, lighter weight, lower cost, etc.). But if you are often landing on harder ground (like I am), then you want to really slow things down.
Where I usually launch the ground is hard sun baked dirt or dry lake beds. Too many times I have wished I'd chosen a larger, slower chute when the rocket hits that ground. Lately I pretty much always take the size that RockSim says to use for a "slow" descent, and then go with the next size larger. It means a longer walk sometimes, but I'm doing a lot less repairs.
my two pesos, s6