The rivalry would still exist between the two
. But personality-wise, I can see how Raphael would make more sense. Though, I think the idea was that Leonardo's departure would be more devastating to Yoshi, being the eldest child (supposedly).
Ironically, Raphael might also have been harder to turn against the family, for all of Leonardo's reputation for family honor. Since Raphael had been separated from his family once and wouldn't have been interested in parting from them again (and boy is
that something that's gotten buried in the sands of time)