A hidden gem
Well, congratulations if you found this information. DeWalt's hiding away of the information on their excellent extension ladders puzzles me - and certainly can't be helping with their sales. But enough about DeWalt's website peculiarities...
These are VERY stable ladders. I have the 4-foot, 6-foot, and 8-foot IA stepladders, and the 20-foot IA extension ladder, and they are simply the best ladders I have ever used - even better than the Louisville ladder that one of the stepladders replaced.
As I understand it, the DeWalt ladders are made by Louisville, but there IS a difference between the Louisville Type IA stepladder that I had and its DeWalt counterpart - specifically, the wider step(s) on the DeWalt stepladders, which really do add to the sense of stability and comfort of use.
The wider steps start with the second step up, with the first step and the top [non-step] - plus, of course, the top itself - being of "standard" width. Thus, the 4-foot stepladder has one wider step, the 6-foot has three wider steps, and the 8-foot has five wider steps. It may not seem like a whole lot of difference, but if you spend hours working on a ladder - hanging drywall, running cable, painting, etc. - the wider steps make a tremendous difference in stability, safety, and comfort.
The "tool top" is also quite useful, with a good array of inserts and indentations, and a magnetized area, for a drill, screwdrivers, nails & screws, etc., further adding to the ability to work long periods on the ladders with a minimum of climbing on and off - and, thus, further increasing safety while also reducing fatigue.
In spite of their stability, the ladders are not especially heavy, and all are easy to move around and place precisely with just one person. (The smaller stepladders are light enough to move with one hand, even while holding tools with the other hand.)
In case you're trying to figure out which length(s) are best for your use, this reviewer (a 6-foot 4-inch 200+ pound individual) uses the 4-foot ladder for general work on 8-foot walls, the 6-foot ladder for working at and above unfinished 8-foot ceilings, and the 8-foot ladder for getting into attics and for outside work. The 20-foot extension is just right for accessing outside walls on a single-story house that's built three to four feet above grade, and it's also tall enough to access the roof.
Pros: Stability, moderate weight
Cons: DeWalt's inability/unwillingness to promote their ladders