One has to be suspicious of the various anchor tests. When I was giving lectures on anchoring, I not only read all of the tests , but talked to many of the testers. Some had "experts" who had dissapeared. Some were definately biased.
If you read all of the anchor tests, you will note that in one test or another, almost every anchor is "the best"--some which were "superior" in one test don't even set in other tests. Looking at the surface, many of the tests appear to be objective, but come up with different results.
Once an anchor has been drug thru a sea bed, the bed is not the same for holding properties. The holding properties can vary from place to place in a test area, even if the surface looks homogenious on the surface.
There are multiple variables in testing.
I also have been a bit leary of the "Hyrdobubble", but have never used it, so I can not testify as to its usefulness. Some of the tests show it does very well.
The real test of anchors is how they do in hurricanes, not in every day anchoring. Unfortunately, we have had a lot of hurricanes in our part of the Gulf coast, and I learned even more than I wanted to know about certain anchor types.
My general experience is that plows are not perticularly good in mud--the Danforth and Fortress types are very good, as is the Super Max. The bubble is to keep the anchor up right--other plows (Rocna, Bugel,& Manson Supreme) use a curved bar over the crown to do the same thing. The bubble would seem to keep the anchor from penetrating, and in many bottoms, the anchor holds the best, if it gets down thru the superficial layer, into deeper and denser layers. (There are those who advocate using cable instead of chain, to get deeper anchor penetration and less "resistance" to burying of the chain, vs those who feel that the friction of the chain helps to hold the boat, and allows the anchor to bury deeper. (For example one Bayou which is a hurricane hole, has mud on the surface, which is very poor holding--in fact a plow will just hot hold in any heavy wind. Next there is a variable layer of sand, and finally clay. If an anchor gets into the clay, it is very difficult to get out. I had to pull a 70 lb fisherman which had held a 55 footer during a Cat 3 hurricane, with sustained winds of 120 mph. This anchor was burried deeply into the clay layer, and it took several hours to work it out--using winches which developed over 3000 lbs of pull, and the boat's engine, working the chain angle back and forth.
Just be sure that an anchor you buy is appropiate for your perticular anchoring bottoms and conditions. Always buy an anchor which will be adequate in a storm. There are some folks who have had great results with this anchor, and others who have not--it probably relates to both bottom and technique.