Think in terms of percentages. This is convenient when you consider an average cadence might be 100 rpm, at least riding on the flats.

A typical 1-tooth cog changes is about 8% and gradually gets smaller as the cogs get larger. At some point, a 1-tooth change is so small it's not of much value. That occurs in the 17-19 tooth range. The flatter the terrain, the more most riders feel the need for the 18T.

I kind of agree that nitpicking 1-tooth increments at the chainrings is trivial since each tooth is only about 2%.

Some people will argue strongly that one certain gear ratio is so "sweet" that they can't do without it. I know for certain that riding the same stretch of road day after day, that ratio will be too high on some days and too low on others depending on the wind direction and strength. There's nothing better about any one ratio than another. I need every one I have at times.

I've read some strange arguments, like using a 39T ring was "uncomfortable" for climbing while a 41T felt just right. This makes no sense to me since every climb is different in grade and wind conditions. Some ratio with a 41 might be okay one day, but not the next. This was a pro rider's comment. I guess whatever works.

I successfully used a 53/39/28 triple crank with a 12-25 for several years, riding in the mountains, but switched to a compact crank 2 years ago (50/34 with an 11-25. I lost my two lowest gears and a little more, but have managed to get by without them. I'm not any faster riding the compact. I've ridden the Mt. Evans hillclimb fast enough to be in the top 5-10 finishers in my (50-59) age class and I did that with a triple. I did spend a lot of time standing in the 39T middle ring, but seated climbing was all done in the 28T. When I read of someone using a 53/25, allegedly for a 7% grade I have to roll my eyes.