Thanks for the info, Todd.

 I do like the SDM  better than the HiViz.  The dot you see is of a smaller diameter with the SDM and more black is seen at the top of the blade above the dot.  Still, the HiViz sight does come with extra fiber optic tubes and a little tool to use to change them out where the SDM just comes with the one fiber optic tube. The HiViz also seems easier to install and remove.  They both have strong points, but I'll go with the better sight picture I get with the SDM.

Scott