Hi Derek,
Just to make sure nobody goes searching through my website looking for something that isn't there, the fact is I haven't done any work comparing side sharpening to "regular" sharpening. I sometimes side sharpen freehand if a blade starts to tip and haven't noticed any effect on edge durability, but that's just ordinary anecdotal user experience, not controlled testing.
I have done some microscope imaging of side sharpened blades and they looked GREAT until I adjusted the lighting 90 degrees so that it brought out all the scratches that didn't show up with my regular lighting, which was optimized to show scratches perpendicular to the cutting edge.
Steve