I would have to go with the T.rex. Admittedly I have a bias because it's the single dinosaur I've studied the most, completed the most papers and research regarding, and still read about the most frequently, but overall the maquette is just more artistically, paleontologically, and ethologically to absorb and muse over. The Carnotaurus is not a widely known animal and in that sense the maquette stands out, but the T.rex maquette is unique because we've simply never had a collectible (or much paleoart at all for that matter) that depicts this animal in this way. It's an older animal though the age doesn't belie that ferocity, but showcases it. Both are wonderful, but if I absolutely had to choose one it would be the T.rex.