I've used both of those products, but the truth is they haven't really been used for a long enough time to weigh in on whether they're "sustainable" for long term use.
When I first started feeding my gliders an "HPW" type diet, I assumed the kit contained the ingredients including the Wombaroo brand High Protein powder. I later learned it didn't after they changed the labeling/name.
The "Kit" does contain a high protein powder supplement (zoo pro brand) and the bee pollen, all you need to add is the honey, eggs, and water. Scramble the eggs in the microwave in 30 sec intervals until fully cooked, add to blender, then warm the water, add the honey and add to blender, then measure the amount of your powder from the kit to the blender, at least that's how I did it. Blend for 2 minutes and pour into freezer safe container, it can be scooped out like ice cream.
The Instant HPW is just mixed with water, it cannot be scooped like ice cream, it's a harder consistency. Most people pre-measure this consistency type liquids in ice cube trays, I use little juice bottles filled with 3 nights worth of feedings for my three gliders, I just find that easier for me, either way is fine.
I personally recommend getting the more well know brand "Critter Love" she is the creator of the OHPW diet and has formulated a diet brand including several options
http://www.critterlovedietcenter.com/original.html