Which would make a better prehistoric monster for this story?

I'm thinking about making a story someday, and in a subplot that I am planning on, there are some kids that are trapped in the main villain's island mansion and are being pursued and eaten by a prehistoric monster, but I have not decided which type would be more suitable. I've been thinking about making the monster be a Tyrannosaurus Rex with a bazooka, but then I have also been considering whether it should instead be an Inostrancevia, a large Gorgonopsid from the end of the Permian period, since a lot of cool prehistoric creatures like this one are culturally invisible compared to the Dinosaurs, but then a quadrupedal creature like that would be more limited in its choice of weapons. Should I just stick with the Tyrannosaurus Rex?