Well, you have mentioned some good points, and I would say Kingdra. As you said, that Electric weakness is pretty bad as of late. Kingdra also works better on a Rain team IMO, due to Swift Swim. Sniper is also a nice option to have.
May I also add that Kingdra was blessed with even stats, making it quite possible for it to survive longer while setting up D-Dance. Gyarados just doesn't have any Defensive Bulk.
Edit: Just remembered Intimidate on Gyarados. Thought I should mention that that Attack lowering ability does nothing against Discharge.
Just as a side note, Bounce isn't really a great move for competitive battling.