I notice the differences (slanted terminals, narrower "A"s, etc.), but had no clue which was which. Weirdly, I'm super-picky about typefaces, but mostly in a "I like what I like" sense rather than a "I know the precise details about why" sense. I dislike both Helvetica and Arial intensely, and so never bothered to learn much about what made them different. They're both just fonts I don't choose for anything.