Originally Posted by
operator
Easier to get to, but more incovenient to use. The shifters are at the bar end where little force is required to make huge changes in steering. Longer cable and housing + handlebar clutter.
Not so with dowtube shifters which are impart almost no force to the direction the bike is travelling. I can't think of a more idiotic and unsafe place to put a shifting unit. At all
I don't know how you can claim that operating a downtube shifter imparts almost no turning force to the bike. For most people, operating a downtube shifter requires removing one hand from the bars while leaning slightly forward. These actions definitely impart a torque on the handlebars that must be compensated. It's similar, but not quite as bad, as reaching for a water bottle - a skill that any competent cyclist can perform safely.
Shifting a bar end shifter can be done with both hands on the bars, so, if anything, it's easier to compensate for any torque on the bars. But that torque doesn't really come from the shifting, since the shifter (if installed correctly) rotates vertically, which imposes very little torque. Any torque is going to be a result of the asymmetric hand placement, which frequently occurs regardless of shifter type.
All of this is trivial for a competent cyclist to manage. Certainly no more difficult a skill than to push an STI lever without applying the brakes in the process.