I'm planning on buying a Brompton, and I am looking for feedback regarding the pros and cons of the stock 3-speed and 6-speed versions as compared with retrofitting a 5-speed SA S-RF5 hub.

What I know is that the 5-speed would give me a wider range than the 3-speed (256% vs. 178%), with an extra low and high gear, and very little weight penalty (only 150 g extra). The 6-speed would give me an even wider range (302%) at about the same total weight as the 5-speed, but with a clunky shifting arrangement using two shifters.

What I don't know is whether the 5-speed hub adds significant drag, or to put it another way, comes with a noticeable efficiency penalty. I keep reading about the inefficiencies of hubs with 5 or more speeds, but I haven't actually heard anything bad in this regard about the SA S-RF5 hub. I would appreciate hearing from anyone who has converted their Brompton to a 5-speed using the newest SA hub, or has ridden 3-speed, 5-speed and 6-speed bikes and can comment on any differences.

Also, am I being unreasonably critical of the 6-speed shifting arrangement? Not having much experience with Bromptons, it seems like it would be annoying to have to shift both shifters just to go up or down one gear. I suspect that I would probably end up staying on the smaller cog for much of a ride until I hit a hill and needed to shift to the larger cog. Is it something that I would likely get used to over time, or is it really as clunky as it looks?