RSTP is a layer 2 redundancy protocol used to block redundant links (preventing a loop), and rate-limit is a switch functionality to limit the amount of traffic that can be transmitted. They aren't really directly comparable, although they can both impact the presence of a loop and the switches behavior during a loop.
Like Jeremy mentioned earlier, if you want to use RSTP to prevent loops on edge ports, you would need to use edge-safeguard/bpdu-restrict (or another comparable STP extension feature on other platforms).
