A tubeless option would be nice, but I'm guessing the average Brompton owner wouldn't necessarily replace the sealant on a regular enough basis.
I tend to switch between Kojaks in summer, and standard Marathons for winter, although a lot of that comes down to running the Kojaks until they really need replacing, then sticking the Marathons from last winter back on, because they're fine! I did have one iffy Marathon, that puncture a couple of times, and then continuously punctured, and could never find the mysterious object that was causing it, but since then, been really lucky with Marathons going long distance between punctures. Been pretty lucky with the Kojaks in the last couple years too, to be honest, but I did have one awful couple of months a few years ago. Then bought a CO2 refiller and didn't have a puncture for months and months.