I don't think it's about fighting amongst each other, but more about how WHM is just a healer who has the tightest MP restriction in the game and SCH is a jack-of-all-trades yet still has just enough healing power to solo-heal the entire game (a case of "if A and B can do X equally, why does A have more unequal dependencies than B). This is why many people feel WHM needs a revamp. It has the pros of raw heal strength and 1 passive party buff, but has many cons like no scaling MP recovery, no burst MP recovery, no active party buffs, limited enemy debuff, no ability to have heals ignore cleric stance, no heals that ignore enemy buffs, no instant heals, limited mitigation, no excess MP to cover for party mistakes.

Ideally the number of pros and cons should be equal for both jobs (but should be in different areas), but since the number of SCH pros outweigh the number of WHM pros, it makes WHM an "inferior" job (not inferior in ability, but inferior in design).