This seems like a bit of a redundant debate... drugs that you make sociable are obviously funner do with people; drugs that you make introverted, alone. And there are just drugs that go fine either way (weed, lsd)
I'd choose alcohol cuz it just sucks on your own basically
I don't use drugs with anyone else, but I prefer to be high on opiates when with other people. It reduces anxiety and makes me more social, but I don't talk much or do much with other people even when I am on opiates. I usually don't like doing things with other people, or talking to them.