Yes, wood is better than plastic but it kind of depends on the chinchilla. My chin doesn't usually chew on the plastic and she's fine with it. Plus she does in fact use her ramps and she has never injured herself on it. I think it the actual cage is made of metal, then it should be fine, since there would be no way out. However if it's made of plastic then I would highly suggest not to use that cage. I wouldn't risk having plastic in it especially if your chin isn't used to plastic and he may eat it. It's really not good to risk the chances.