All mine wear collars, for me it is peace of mind that they have a tag and collar on just in case they slip outside one day because I would freak out.. they are indoor only. But they also wear collars because I am a collar freak, I LOVE picking out and buying new collars especially ones with jewels on them haha, it's almost become an obsession.. I buy the little charms to put on them too. They all love wearing their collars though.
The trouble with collars and Ragdolls is that not only can they be dangerous but also they damage the fur around the neck making it flat or breaking it. It's a definite no no for cats that are to go on the show bench. None of my cats have collars, but then again none of them ever go out either.
We had a springer spaniel who was tattoed in his ear before he came to us a 9 weeks old but unfortunatley, as he grew the tattoo became more and more obscure until it was totally indistinguishable so that didn't work either.