So I imagine the answer to your question would be, about as different as they can get. Why bother with these crazy sects and false teachings? It leads not to greater understanding, usually it leads to arguments. Mainstream Protestants are hard enough to deal with, but at least there is a sort of “detente” we have with them, we don’t feel the need to engage in constant battling apologetics. These extreme groups are usually very misguided and very narrow-minded.