How sharp is sharp?

Rob Cosman recently posted a video which purports to show why it is worth sharpening planes to 16,000 grit vs. 1,000 grit.  In the end, the only difference he could identify after planing a piece of hard maple was feel: he felt that the 16,000 grit side was ready for finish right off the plane while the 1,000 grit side wasn't.  He also alluded to but did not demonstrate superior performance on figured wood.  That's it.

I use diamond stones followed by honing compound on a leather strop.  Comparisons are difficult and sources differ, but my EZE LAP SF diamond stone is 1200 grit, a bit finer than the coarser waterstone in his test.  The particle size is about 11 microns for the former and 14 microns for the latter.  The 16,000 grit waterstone has a particle size of about 1 micron and produces what is commonly called a mirror finish.  It is apparently about like using green honing compound on a strop or 1 micron diamond paste.

I had several reactions to his test.  First, I think his test may have been a best case for the 16,000 grit waterstone since he took just a few swipes with each plane before feeling the surfaces.  I have read that the 16,000 grit edge will degrade quite quickly and I wonder if the difference between the two edges wouldn't be a lot smaller after even moderate use.  My second reaction was that this isn't much of a difference the way I work.  For a variety of reasons, I normally scrape or sand my surfaces lightly before finishing.  Would the finer stone make a difference if you scrape or sand before finishing?  Third, I am not sure what impact limiting the test to hard maple has.  Fourth, there are a lot of choices in between these two grits and I wonder how they would stack up.  Finally, even if you believe as he does that it is important to hone to a mirror finish, wouldn't the case be limited to the plane you use for final smoothing or for figured wood?  I would certainly not bother on the No. 5 I just used for fitting screen doors.

Thinking about this subject brought to mind a related question, which is this:  if you want to hone to a mirror finish, what is the best medium?  I often feel that I don't gain much by using green honing compound on a leather strop.  Maybe it's for the reasons I have suggested above or maybe it is because the honing is offset by a slight dubbing of the edge, something you read happens quite often.  Given that I won't use waterstones, what might be better ways to hone beyond my SF diamond stone?  I've come up with two alternatives I am going to try.  The first is to use green honing compound on something other than leather, say mdf or a piece of wood planed dead flat, in an effort to avoid dubbing.  The second is to use a steel honing plate and diamond paste, which is available in 6,3 and 1 micron versions.  This is much less expensive than a comparable waterstone, the plate stays very flat and the paste lasts a long time.  Lee Valley suggests that you can use mdf or a flat piece of hardwood for the diamond paste as well, but the steel plate is inexpensive so I don't see any reason not to buy one.

The bottom line for me is that it doesn't take a lot of extra effort to hone to a mirror finish so I might as well do it, so long as I find that the edge doesn't degrade so quickly that it is a waste of time.