I've watched Series 1 of both the American and Australian versions and series 2 of Australian Traitors, which I loved.
The American ones as PP have said, have Alan Cummings as the OTT host. Great fun and wardrobe were very busy for him. They're shot in the same castle.
Series 1 and 2 Australia use a heritage hotel and their host is an actor, but I didn't know him. He seems to make more of an impression in Series 2.
The American two and the Australian series 2 have a mix off regular people and so called well knowns, either from other reality TV programmes, an actor and people who've hit the headlines for other reasons. I haven't known any of them, so it hasn't made any difference to me, although a few of them have had overwhelming personalities. You only get them in relatively small doses though.
I think it's interesting to see the other countries series and compare them to how the game's played here.