Help..Need advice for tux for little ringbearer

My little godson/nephew will be our ringbearer. He's only going to be 1 1/2 years old ... wearing about a size 18-24 months. I was recently told for that size, it would be best just to buy the tux for him, which would be about $80 as opposed to the $100 rental fee. Is that true? Or should I keep shopping around? We will be renting five tuxes, not counting the ringbearer .. so we would be entitled to a free tux, which can either go to the groom, or half to the groom, and half to the ringbearer. What's everyone's gut feeling on this? Buy, rent or shop around?