The iPhone XR runs on Apple's 2018 A12 chip with 3GB of RAM, while the iPhone 11 runs on 2019's A13 chip with 4GB of RAM. Apple doesn't list how much RAM each phone has, so the RAM number is according to GSM Arena.
It's tough to gauge the difference the iPhone 11's specs will make. New iPhones are always more powerful and faster than older iPhones, but the performance gap between the old and new is narrowing more and more every year.