Unsurprisingly… Brompton.
However, I've got three, T6 (effectively an M6R), S6L and S2L-X.
I prefer S type handlebars, faster and less bendy, but the M let you use bigger luggage on the front. So it would be an M.
The 2 speed is nippy in town because of the flying start acceleration but the gears are 56" and 74" which is a wee bit short at the top end so I'd probably get a standard ratio 6 speed.
I don't use the rack for carrying stuff much but it's handy when you need it and you can put nicer rollers on there for hurling it around when folded so thats R with easy wheels.
The X option adds a few hundred to the price but you don't get corrosion on the back end or the forks.
I like a SON hub and lights.
Funnily enough the one on order from BikeTrax is an M6R with easy wheels and SON. It's not getting the X bits as that would have pushed the memsahib over the edge.