I think the 6-16826 is command control only without the manual wired switch to control it as well, and the 6-81953 has both the command control and the wired manual switch control.
http://www.lionel.com/products...ol-lh-switch-6-16826
http://www.lionel.com/products...ol-lh-switch-6-81953
The command only (? because I'm not sure they were actually delivered without a manual controller) is $10 more and an earlier product. I find it confusing too. Buy the 6-81953.