I have a S6L and on reflection I wish I had never gone for the 6 speed. Unless you intend to really tour extensively on your Brompton you do not need the 6 speed. Also the changing between the 6 gears is just awkward, make sure you trial ride one first. The S bars are by far the best ride if you like to go at speed which I do, the M bars are to sit up and beg for me. The rack is essential and the easy wheels make life much easier.
I have a S6L and on reflection I wish I had never gone for the 6 speed. Unless you intend to really tour extensively on your Brompton you do not need the 6 speed. Also the changing between the 6 gears is just awkward, make sure you trial ride one first. The S bars are by far the best ride if you like to go at speed which I do, the M bars are to sit up and beg for me. The rack is essential and the easy wheels make life much easier.