You can put the tags on the harness, and a harness is so much safer!
You don't have to keep it on him at all times, unless you want to...If you do, I would recommend getting a harness like the silk ones that Chattiesmom makes so that you don't have too many problems with mats in the hair.
There was a member a long time ago whose dog, I believe, hung itself with collar
It was extremely sad...Also, I can't tell you how many times we have heard horror stories about collars causing damage not only to their tracheas but also wiggling out of part of the collar and getting it stuck in their mouths...