On the grass
My previous pair lived until 9 and half years old! They lived outdoors ALL the time - Winter and Summer and had a fixed sleeping hutch raised off the ground within a large moveable and totally fox - proofed run! The sleeping hutch has an access ramp, and they can come in and go out as they please - and now my new pair are also very happy and healthy out there. We do have a temporary divider for the male as 4 babies arrived 5 weeks ago! The babes also love it out there and are very healthy, they left the nest of their own accord at 3 weeks and chewed grass gradually and they make a fantastic lawn mower!! We move the run daily and have only ever brought buns into their main hutch if an extremely hard frost was forecast. When it snowed when the babes were a week old mum simply pulled more fur out to keep them warm. In my opinion the outdoors life is great and natural for rabbits and they live long and healthy lives. It is also a lot cheaper! They have a few pellets now and then to supplement their diet of grass, dandelions and lots of veg peelings / left overs! (Although obviously due to mum feeding right now and babies growing we are giving extra pellets.)