The question still dogging me “which side is stronger?”

Over the years, I’ve seen and read many online friends and others, slowly creep along the change spectrum; crossdresser, gender fluid, trans woman. “That will ever happen to me”…but now I see so many similar patterns developing. 

Michelle asks the question, "which side is stronger?"  Although she doesn't mention "the slippery slope", it does make me wonder just what the science is behind the progression she describes in the paragraph, above.