Personally I'm not comfortable with lone bunnies being outdoors as they are social animals and even with lots of attention, they are still probably looking at 22+ hours a day alone
Having said that - my bunnies are outdoors in pairs and they absolutely love it - I rarely interact with them, I get pleasure just from allowing them to be bunnies, so I think indoor or outdoor should depend on the number of bunnies and the personalities and preference of the bunnies and how you interact with them.