The document compares the sizes and features of Brachiosaurus and Stegosaurus, two dinosaurs that lived about 150 million years ago. Brachiosaurus could grow up to 75 feet long and weigh 50,000 pounds, making it significantly larger than Stegosaurus which reached only 30 feet long and weighed 10,000 pounds. The document concludes that in a fight, Brachiosaurus would likely defeat Stegosaurus due to its massive size advantage and ability to use its long tail as a weapon. Sources used for the comparison are cited.