It's quite a difficult decision, mine are indoor cats just cos i feel happier knowing they are safe, but I take them outside occassionally on a harness, so it's up to you how you feel. We have 2 cats to keep each other company and they do play together sometimes but aren't close, i don't think they'd be hugely bothered if they were to be on their own, but i like knowing they have each other during the day. It's all down to personal choice, how much room you have in your home and the area you live in.....