I think that it looks like a copy of Marlin's SAS kit, which was a copy of All-Pro's SAS kit. Until I see something original come out from Trail Gear that command the same respect from me at Sky Mfg does.
Speaking of which, the problem with his hanger is that it is C-channel, not boxed. If that isn't a recipe for disaster I don't know what is.
When it comes to the front hanger, there's only so much you can make different. The difference is in the details.
All Pro seems to use a big square tubing than either Marlin or Wally-Gear to tie the two spring hangers together, which is probably stronger in that area. Also, A/P seems to be the only one using the bolt hole method to line up the front spring hanger to the front cross member. And A/P does have a tiny extra gusset that I don't see on the others. All three are well gussetted at the spring hanger itself, which I like.
The thing I don't really like about FRORF's hanger is the lack of gussetting at the hangers. It's probably the cheapest design to manufacture, too. Although he does include front brace brackets as addition gussetts to weld for the front hanger that others don't. And his hangers are 1/4" steel. Not sure about the others. I do like the fact that FRORF seems to be the only one who at least addressed the difference between IFS and SA trucks as far as front crossmember hieght and how that affects the over all lift.
Sky's is a wierd design that looked like they made it mainly for advertisement. They probably wanted to use a flat piece of steel that they could stamp out their name, then roll into a C-channel and weld hangers too. It's probably hard to stamp in their name on a piece of square tubing. I don't really like the design, either.
Now that I look at all the hangers again, I can't really figure out how one gives more or less lift than the others. They're all basicly the same design as far just shackle hangers with some kind of brace in between. The hieght differences between the top of the shackle hanger the bolt hole can't be more than a 1/2" different between any of them. And is probably less than that.