I have never tried STI shifters but I have barcon shifters on one tandem. They are ok but I don't like the placement outmost on the bar as it interferes with the handling of the bike (balance). I actually like the downtube shifters on my old single better but they should have been too far down on the tandem.

On the tandem I bought last summer I have SRAM rear mech so I put SRAM ESP shifters (Gripshift) on the Yakuma bar that I had initially. I did NOT like the Yakuma bar but I did really like the Gripshifts! I'ts the best I've ever had or tried. They are very robust and the gears just clicks in. With the front mech you can fine adjust if there is chain rub. The mechanic on SJS Cycles that built my Thorn Adventure said after the test ride they always do that the gear shifting was extremely smooth!

Well what to do when I couldn't go on with the silly Yakuma bar and wanted to have a real road bar and the grip shifts was impossible to fit on the road bar?

The solution I found out was to install a SECOND handlebar below the road bar on the ahead steerer. Thoughtfully the mechanics at Thorn hadn't cut the steerer. So I have put a second shortened straight MTB bar below the road bar and on that I've put the Grip shifts and the thumb shifter for the Arai. I do also put the handlebar bag on this short bar.

This works VERY well. The only disadvantage is that I sometimes have difficulties seeing the gearing numbers. So the answer to the question for me is not STI or bar end shifters but SRAM ESP shifters! The non ESP shifters will fit Shimano rear derailleurs also but for front shifters it doesn't matter.

Per