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.