Bottom line: pick London for free world-class museums and easy English navigation; pick Paris for iconic-sight density and French aesthetic. London's British Museum, National Gallery, Tate Modern and V&A are all free — enough to fill three full days without touching your activity budget. The city is a patchwork of distinct neighbourhoods (Westminster, Shoreditch, Notting Hill), and the Tube is all-English with intuitive zones, making arrival easy for first-timers. Paris wins on compact, concentrated landmarks — Notre-Dame, the Louvre, the Musée d'Orsay and the Tuileries all link on foot — but major museums charge €17-22 per entry (free on the first Sunday of each month). Budget-wise London runs slightly pricier day-to-day, yet Paris restaurants surprise people (a two-person dinner with wine in the Marais runs €80-120). Want immediate wow → Paris; want a slow, deep explore → London.