For touring, toughness would seem to be priority #1 if the distances are appreciable and/or the travels are to remote places.
I don't know of a tougher unit than a Shimano MTB derailer. These can be re-badged and even the mid-cage units like the one pictured below will handle a wide range of gearing.
For friction-shifting I prefer a faster action (greater actuation) so will route the cable to the wrong side of the anchor bolt. In conjunction with modern derailer cable housing this does give me the instant slap-shift action and with the lever not having to move through such a wild range of angle.
The best shifting I've yet experienced was a Duopar on my Trek 710. Symmetric shifters, an AT triple and a modest-sized 7s Uniglide freewheel somehow created the perfect storm of instant shifting all of the time.
I went with this setup on my 1967 Steyr-Sears Ten-Speed when the original Simplex derailer showed signs of excess wear, again with the cable routed for greater actuation:
