Verified answer

Depends really. If you add Lanturn to your team, you will have 2 Ground weak pokes since Typhlosion and Lanturn take super effective damage from Earthquake. If you pick Lapras, you have 2 pokes weak to fighting type attacks (Lapras and Umbreon). Good thing is that Dragonite resists both of these attack types, so really it all boils down to personal preference.

I honestly find Lanturn to be more useful than Lapras as it can learn Thunderbolt, Suf, and Ice Beam which gives it amazing coverage against a majority of pokemon found in the game.

I'd often go for the Slowbro. It's very bulky and much more trustworthy, IMO, than Slowking. Slowking has good precise defense in comparison with Slowbro's just right safeguard, however seeing as most of its weaknesses have a massive designated assault pool (electric, grass, bug, ghost, darkish), i would not waste my time on a Slowking. Lapras is very well too. It can be no longer used lots so that you maybe equipped to surprise anyone with it. Hold in intellect that it can be ice style too, so you would have just a little of form protection problems with Lapras. Golduck is just too "jack of all trades" to be of a lot use. It has very well stats dispensed particularly evenly around the whole thing, so it is not going to excel as a valuable member of your group. EDIT: LOL, I took a look at your answers and realized that everyone gave you yet another opinion XD

Lanturn Crystal

Lapras because it can learn ice beam which will be very useful when you fight Lance in the elite four.