Based on their in-game status alone, I’d say Erliphosaurus. They’re really similar after all, but Erliph is a Legendary hybrid with a tournament-exclusive ingredient, so it outranks other Legendaries like Indominus, which has a more or less equal ranking to Diloran in JWA.
From what I remember of Erlipho, it’s also more on the tankier side, rather like Diloran in that aspect too.
Perhaps Erlipho could use its brighter colours to startle or stun Diloran long enough to gain the upper hand? It is a bit more showy than Diloran, although the latter’s sail is bigger (if Erlipho’s feathery ridge counts as a sail). But feathers generally allow for mobility, allowing for a more effective threat display, even in its level 1-10 form (I don’t think the successive stages should count, since Indom in JWA is the level 1-10 Indom from JWTG).