SnoSeal works best if you melt it at about 145 degrees (I use the oven when the wife is not watching) and apply it as a liquid to clean, warm boots. However, even SnoSeal will have to be reapplied if your boots are exposed to a soaking. Also, don't expect SnoSeal to keep your feet absolutely dry. GoreTex will do that, but all SnoSeal really does is keep the leather from absorbing water.
I have used the heavy duty Scotchguard on a variety of clothing articles and I don't suppose it is too much different than the Atsko Permanent Water-Guard. The Scotchguard works really well.