Mine have never worn collars, and they too are all microchipped.
I know all the pros but experienced a very big con with a break away collar. Mi Tu caught her paw between her neck and the collar and was struggling when I found her. That was the last collar any cat of mine wore. They are now microchipped if they are inside cats (I'm not sure how much good that will do given my circumstances but it makes me feel better).
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