We did not particularly care for the trigger/sliding shifter of the Brompton. Mind you, we have not tested the grip shifter for a comparison. Our impression was that the Brompton shifter was a bit awkward to use and aesthetically unappealing. -invisiblehand

I personally don't like the trigger on the B. I do like the twist grip on the Merc and it is lower profile and more positive to use for me...
.....regarding repairing SA hubs, they tend to last a long time with minimal maintenance. I have yet to have any issues with any internal hub I've bought. Look at all the SRAM 3X7's on the road and they've had no issues that I've seen. Internal hubs just aren't as popular in the US and Canada as they are in Europe. For a commuter bike it is far and away my preference. -Wavshrdr

Completely agree with what you say about the twist grip gear change. It is very neat and positive. -EvilV

The ugly Brompton shifter was taken off and replaced with something I liked far better-a traditional metal three speed shifter I kept as a spare for my other 2 bikes. The gear selection is clearly marked (1, 2, or 3), the shifting stick lever is small and non intrusive, and when and if the unit breaks-I get another one and replace the whole unit-rather than playing with little awkward parts. As for it's chances for failure, I still use a shifting unit from 40 years ago! It is still a matter of what works for the individual.

The most important part of the drivetrain is the hub. Those AW hubs are the best for the type of riding that I now do-commuting. The derailleur bikes I had up until 2 years ago were more of a headache than a help even for the hills surrounding me. I do not miss them at all.

...they have braze-ons the forks for the mounts. You could have this done. There are places that do this. The Kool-Stop (Salmon colored MTB) pads will help too. This is very important to get the salmon colored MTB pads. You have to juggle them a little getting them in there and due to the small diameter rim they have to be aligned perfectly but what a great improvement. We go from marginal Brompton brakes to at least adequate. By adequate I mean they will actually slow you when needed but if you are heavily loaded, touring and in the hills I would still exercise caution.
...The upgraded brakes on the Merc GT6 will stop on a dime and give you change. EV, another upgrade that will help is possible better levers in general. I don’t know on the Merc GT3 what they have but if they are like the C model Bromptons they are pitiful and pathetic. The higher end Brommies levers are better than the C models but still not great. -Wavshrdr

My "pitiful and pathetic" C Brompton has undergone a transformation. The most hated part of the bike (yes the brakes for me) has went it's first transformation. I have not decided on the braking system that I think would work for me, so I simply did some slight improvements on the stock brakes until I decide on the new braking system I want and would work as well as my Boardwalk's does. A brake pad change (Kool Stops) and rotating the levers up a bit helped greatly for comfort and stopping power, but I will not take it out in wet conditions or do much in the way of hill riding until I find what I want. The Merc's appeal of better brakes up front does not do much for me as I am not too keen on being too brand loyal or buying a bike based on just one or two parts. I still like to experiment on other makes of components to better reflect my needs-and continue to buy steel framed bikes only.