I hate extract sauces in general. I can't stand the flavor. Some say only the "keytone extracted" ones taste metallic, but to me all of them taste pretty ass-y. I can deal with Defcon Zero because I think he does some kind of alcohol-and-boil-down process which is OK, but in general all of the Dave's and CaJohn extract sauces just scream I TASTE LIKE EXTRACT when I smell them, even.
That said, and as someone who has tried both Mongoose and Black Mamba, I'd say that Mongoose is the more edible of the two. Black Mamba was hot, but tasted like nothing but extract. Mongoose actually tastes decent and mixes with food better while still having insane extract-level heat.
My favorites of CaJohn's sauces are Scorch and Fatalii Fire. Mongoose is a ways down on the list, though at the top of the list of sauces that contain extract.
