For the first, I'd be alone, hands down. I find most days that I don't want to be bothered outside of work. I wouldn't mind it so much. Having someone there 24/7 just sounds awful. Sometimes it's bad when my roommate constantly bothers me. Besides, I want some privacy. :(
As for the second? I guess the light. I'd like to be able to see what I'm doing. Otherwise I'd probably be a klutz! Darkness doesn't sound that bad in theory, but I'd probably go bonkers after awhile.