saccattack

"the more reliable one" for Dragonair and the Dratini with the most HP.
Unless one of the Dragonair's has an amazing PokePower, I'd just go with whichever has the most HP or can do the most consistent damage.
(I.e. I'd use a LL for 30 over an LC for flip 3 coins and get 20 per heads)

The Metal/Lightning variants. Although you can use either, Mekkah and I only use the Lightning variants for consistency in case you can'y pull dragonite and need to attack, so that you won't be short on energy. as I said, you can customize the deck quite a lot, since all it relies on is you getting Dragonite in play to keep Metagross charged.