"Porter has now come to mean a dark malt liquor, made partly from brown or black malt, the caramel in which gives it the sweetness and syrupy appearance, and containing four or five per cent. of alcohol. Stout is a stronger porter, with larger amount of dissolved solids, and containing six or seven per cent. of alcohol."
"A Hand-book of Industrial Organic Chemistry" by Samuel Philip Sadtler, 1900, page 196.
It's official. Stout = a stronger Porter. I hope that settles this question for once and all.