IMHO regardless of the flowrate, 1 of the main reason is how fast the the waste is clear to the Sump once it is produce by the fishes, some tank setup may take half an hour due to the return pump used whereas others may take much longer becoz of a lower output pump.
As it maybe quite unsightly for some to see the waste floating around, some just don't mind, from my understanding, once BB's are mature, it would be quite difficult to flushed them out with a fast flowrate than again i maybe wrong
Personally i prefer a faster flowrate, debris get cleared faster but in terms of BB's maturity, mine took as long as 6 - 8 months for a 5' sump, at least that's what i felt when i see my fishes and water.