It depends on rider, terrain, and (basically) where you "spin" out and where you must get off the bike and push.
The 800 Sport "Frankentrek" came into my possession as a 7 speed triple. I was a 250 lb, out of shape carni-sugar-vore who began riding in the foothills of NE metro Atlanta. At that time, a hill I would sprint up today, needed more than the original granny and first could produce. At the same time, Big and 7 resulted in occasional coasting....
Ignorance and necessity led to replacement rims with a 9 speed cassette. Health benefits began to kick in, though best practices were still a mystery. So, 8/9 rarely used, but hills seemingly easier. Fast forward from mid 2010's to last year, and another opportunistic replacement... this time, a lower toothed triple.
Now, at 175-180 lbs, having ridden 6+ years, and in great shape for 58, I find myself using all the gears regularly, with mathmatical overlapping of some combos. With where I am at, physically, need-wise and geographically, I would say my triple-9 is meeting my needs! At the same time, by math and by feel, a double would be doable. But, for all the above, cassette 9 is fine
