You have said it. Thor is faster. Not to mention, on average, Thoradolosaurus will be able to land 2 to 4 hits. One WILL crit with such a high percentage if 3 hits are possible (in my experience).
Allosinosaurus have worse skills (armor piercing instead of shattering, impact instead of rampage). But it is more beefy with more health and armor.
That is what being balanced is. Thor has higher damage output and is faster, Allosinosaurus is tankier. That is the deal. You can decide what do you want from your chomper and invest accordingly.