This image is just for a question and not like one of those 'vs' images i use to post. If that is the case then one member from the dinosaurs group is enough to completely destroy the mammals group and that is Apatosaurus.
Ankylosaurus could likely cripple that indricothere with a single swing of that tail club.
Carcharodontosaurus couldn't get in close enough to attack Megatherium without getting slashed by those claws.
...H. gorgops would devour Spinosaurus in one bite.
Because they're much more ancient & adaptable...
And they too are still alive !
Dinosaurs were the dominant species for 160 million years, so far mammals have only been dominant for 50 million but the combined IQ of all those dinosaurs is about the same as one elephant so it depends on what criteria you are using.
Interestingly Mammals get bigger at high latitudes but Dinosaurs & reptiles get smaller?
the mammals might have a chance
But in adaptability, us mammals have the edge, and in the end,
Its survival of the fittest, of those who can adapt,
Thats why Mammals have survived so much extintions,
Although Im a bigger fan of Dinosaurs, I have to say, that mammals are superior