Is there a good reason to switch a baby's pacifier?

My son uses the Nuk starlight pacifiers only for naps and bedtime. He currently uses the size 1 (which is supposed to be up to 6mo). Now that he is older than 6mo (he's 10mo now) should I have switched him to the size 2? Are there any benefits to moving up to the next size? Or is it better to stay with the smaller one?