Actually, I recently heard that there is no pattern to whether males were larger or females were larger. But yeah, as you said, it's safe to assume males were larger. I usually do that if I'm unfamiliar with the species.
Hmm, I wonder if Sue, that T-Rex I mean, was in fact male. Might have been.
Anyway, back on the original topic.
For strongest, I would say either Sharptooth or that male sauropod that Sue meets For smartest, definitely those rainbowfaces Littlefoot meets. As for fastest, probably Ruby's species or Ozzy and Strut's species.