Both dinosaurs have its strengths and weakness' such as the velociraptors sharp teeth to cut through its prey's belly, or the stegosaurus' thagomizers; which could leave fatal wounds.
I think that the stegosaurus would win because mainly of it's size...
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| velociraptor compared to human |
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| stegosaurus compared to human |
Even though the average speed of the stegosaurus is 7km/hr and the velociraptor's is 50km/hr, the stegosaurus could pivot its legs and stab the velociraptor with its thagomizers.
Bibliography
http://www.sciencekids.co.nz/sciencefacts/dinosaurs/stegosaurus.html