Benchmarked strictly across TripTiming's 5 empirical pillars: Crowds, Weather, Vibes, Prices, and Safety.
London emerges as the optimal May destination with an overall TripTiming Index of 61/100 vs 55/100 for Paris (+6 point advantage). London experiences substantially lower visitor footfall and shorter landmark queues (heavy visitor congestion vs peak seasonal crowding in Paris). Urban navigability is also slightly smoother and more predictable. Travelers also benefit from lower accommodation costs (~$342/night vs ~$377/night in Paris, saving ~$245 over a week).