I have used PS products for the bulk of my diesel life (last 25 years).
Recently though, I started using Howes because it was the cheaper of the two at my local farm supply store (found a great deal!).
I have not been able to quantify a true performance difference between Howes and PS and Stanadyne.
This summer, I pulled my travel trailer nearly 4k miles out to Yellowstone and back. I experimented with Howes, PS and such for different tank fulls. I even tried the two-stoke oil thing. There was not a really good consistent weather/road pattern, but regardless, my mileage didn't seem to waver much no matter what product I put in the tank. In short, they all performed about the same.
I personally look at the additives as something that is a smart thing to do, because lubricity is but one advantage of these multi-range products. They also address moisture, cetane, cleanliness, pour-point suppressents, etc.
But I also don't know that there is a clear "winner" among them. Yes, the lubricity study does have some interesting data, but it also ONLY addressed lubricity, and not any of the other attributes these products offer. Therefore, while one might be the "best" at lubricity, it may flounder at pour points, and we'd have NO idea, because the study does not address that issue. You cannot say that one is "better" than another when ONLY one characteristic is chosen. These products are multi-tasked, and very capable.
In that sense, I believe that all the major brands offer performance good enough to warrant their purchase, so I typically choose the least expensive. Howes, Power Service, Stanadyn and such all are easily attainable, and do a job well enough given all the topics they address.