my preference would be for some wider gaps in the low range and closer in the high*. Dropping down from 2nd to bottom doesn't always feel much of a difference, but sometimes going 13 to 14 feels a huge gap. Not having the perfect higher ratios doesn't really matter riding solo, it can make it harder staying in a group.
* My preferred 11-28 9 speed cassette (When I used such things) had over 16% gaps at the bottom and under 9% at the top.
Agree with that. When I ran derailleur gears I generally had 2 or 3 close gears at the top end of the range with 1 or 2 tooth gaps, then progressively wider at the low end.
I've done something similar on a recent conversion on my 2009 "light" Brompton, to mimic the recent Brompton "P-line" model that has 4 derailleur gears.
Although I prefer the S5/2 hub gearing for robustness, reliability and low maintenance, a lightweight wheel and a limited number of derailleur gears makes it easier to carry, an important factor as I use this bike mainly for short urban trips and often carry it into buildings or ferries.
By combining this change with a couple of other mods I knocked about 1 kg off the weight, not important when riding but it makes a big difference when carrying the folded bike.
I currently have six sprockets - 27,19,17,15,13,12
Two close gears at the top end, 3 reasonably close gears in the middle, then a big jump when I need something for steep hills.
Slightly more overall range than the S5/2 configuration, and more useful gearing on the flat. The trade-off will be more maintenance, and almost certainly more frequent chain and sprocket replacement.
