There is really no difference...the hempy bucket has roots sitting in stagnant water...my roots sit in stagnant water. At least my stagnant water changes with each watering. The hempy pot has a "dead zone" that doesn't change much if at all.
The difference is that there is less evaporation with the water in the bucket.
You don't want to feed or water your plants in hempy till they have used all the water in the bucket so there shouldn't be any dead zones as you put it and when you do feed you want to make sure that you get run-off to keep it fresh.