What we know is Yoshies are a race of dinosaurs similar to the Struthiomimus, right? I completly agree to the Male Laying eggs theory, because in Mario's world, or, more specifically, Dinosaur Land, where Yoshi's Island is located, the evolutionary ladder seems... crooked... although what makes a male is usually the ermm... lack of Uterus, as for Yoshi's testicles, Mario is a kid Icon, and so is his buddy.
Rah, Rah, can't you see?
Now the winner is yo-shi!
*attempts a high kick*
AAUUGGHHH!!!!!
*falls over*