IOTA 2.7 Billion supply. You cant compare it with xrb.
Total Supply is mostly an irrelevant factor IMO.
Even tho I don't get end goal of XRB. So far we know no fees not just another bitcoin clone. Apart from this. I am just waiting for future plans. How it can be used just like btc. Lets see what happens after 100% distribution done. Mean while dev's will keep fixing sync issues.