I've used them both. They aren't comparable though... Wonderslim is
more a fat replacement, not a egg replacement. More like baby food prunes
& another product called Just Like Shortening (I believe Wonderslim is
plums + lecithin?).
Very important baking tip with Wonderslim (or similar stuff), is to
NOT OVERMIX. Things get rubbery fast. I also try to use whole wheat
pastry flour instead of regular flour, the pastry flour has lower gluten
content and will not get as rubbery.
Another plus (or minus) is that the fruit purees are sweet & do have a taste
of their own, so reduce sugar and don't expect them to work in most "light"
things like a yellow sponge cake. Works great in chocolate things though.
I gradually just went back to using applesauce, since it's easier to finish
a jar of applesauce after baking with some of it. A jar of Wonderslim
would go to waste after using half.
I also have a box of Ener G and have mixed feelings about it. It works fine
in some things but IMHO those were things that really don't need egg (whites)
in the first place. I still use egg whites sub'd for whole eggs when I bake,
either real egg whites or dried powder form.