I’d agree with Jo having been to both with a toddler. Barcelona also has loads of little playgrounds all over the place so you can break up whatever else you are doing with a visit to these to burn off some toddler energy. Park Guell - but book!!! Also Spanish people love children, just didn’t get the same level of warmth and frankly acceptance eating out etc in Paris with a 2 year old.
I'd agree, Barcelona 😊
I've been to both with my little boy. Paris when he was 3 and Barcelona when he was 1. Paris isn't very toddler friendly unless you are planning disney land. Barcelona has a beach, aquarium, fun architecture and is a lot more kid friendly.