Apples and oranges : Ubuntu is a commercial endeavour with a huge entreprise desktop and server base (not unlike redhat), while Fedora is the testing grounds, community-side of said redhat, so inherently not made for IRL work.
I'm pretty sure a lot of people use Fedora for work (I do, on my Asahi macbook), but if you are a business you probably won't, as you'll look for something with available customer support.
All other merits and demerits enunciated here are valid, but the true difference is in their target audience.