Many drop handlebar bikes come with new style integrated shifters; the gear changers are an integral part of the brake levers.
Though convenient to use, integrated shifters will be nearly impossible to repair or replace in the developing world. Also, they won’t continue to shift smoothly when your drivetrain has more than minimal wear, so you’d need to replace drivetrain parts frequently. This is difficult to impossible on an extended tour in the developing world, and more frequent drivetrain replacement increases your maintenance costs.
Bar end shifters, though not quite as convenient to use as integrated shifters, are more repairable and continue to work with a well worn drivetrain. The rear shifter on our Surlys can be easily switched from indexed to friction mode, which allows more flexibility in riding an unevenly worn cassette or using locally available parts which might otherwise be incompatible. The front shifter operates only in friction mode.