Dirt 5 on Xbox Series X – what's the difference between 60fps and 120fps racing?

From Digital Foundry: “What makes the next-gen difference? Today, the embargo lifts on our first look at an actual Xbox Series X title – Dirt 5, from Codemasters Cheshire. Xbox Series consoles benefit from three plays modes, including the ability to play at 120 frames per second on compatible displays – and first impressions are highly favourable. What we’re looking at today isn’t a final build and optimisations are ongoing up until release on November 10th, but the developers look set to deliver an involving, fun driving game that gives the user plenty of choice in how the generational leap in CPU and GPU power is deployed.”