These two are in the same family, so the differences are in the detail.
Acinonyx jubatus
Panthera leo
Build is distinctly slim, with a deep chest, long limbs, and a small streamlined head.
en.wikipedia.orgCoat carries around 2,000 evenly spaced, solid black spots each measuring roughly 3 to 5 cm.
en.wikipedia.orgAdult coat is plain tawny with no spots or rosettes; cub spots fade by adulthood.
en.wikipedia.orgTwo solid black lines run from the inner corner of each eye down to the mouth.
en.wikipedia.orgMales carry a prominent mane covering the head, shoulders, and chest.
en.wikipedia.orgTail ends in a prominent bushy white tuft.
en.wikipedia.orgTail tip carries a dark hairy tuft shared by all lions.
en.wikipedia.orgBoth are recorded in 3 of the same grid cells across Namibia, so a sighting in that overlap could be either.