Pretty much agree although I've seen a pic of one of Phil's Merts and it had purple verrucae.
Anyhoo, yes, generally, orange verrucae for Merts, but also merts verrucae (whichever colour) run all the way down to the pedal disc, whereas they stop mid point (ish) down the column in Gigas. Gigas generally blue/purple verrucae
Giga tentacles will usually taper, where merts will end bluntly. Merts sometimes exhibit longer tentacle area around the mouth area.
Hads generally don't exhibit verrucae.