both.
If you use the Malthael set, equip all pieces except for the weapon. This will give you enough for both Flamestrike and Hailstorm procs.
The weapon want to use is a crafted Crystal Sword with
ideally Cataclysm proc and Banish proc + Kraken Stance oskill. The Cataclysm proc on its own is amazing but combined with Banish all your spell damage does truckload more which also works in conjunction with Kraken Stance. Combine this with a Bear Stance Paladin shield (Best stance until mid-late game. Kraken isn't required until late game or for this build to succeed in any way it's just free dmg). This setup even without kraken will give you more damage than the full Malthael set which you gradually get rid of as you progress to late game anyway.
used a spiritual shrine but i rolled the impossible so it just became my bis (excluding sacred uniques)
As of 1.4 there is a new weapon called "Cold Blood" which has +20 to Banish which can be further scaled with +All skills however requires +1000 dexterity to equip (use -req jewels). The banish on the sword is incredibly powerful and I would recommend using this sword or on switch if you are unable to roll both Cataclysm and Banish on Crystal Swords.Additionally if you get Kraken Stance along with these
two procs (Cataclysm + Any other proc is fine if you have Cold Blood on switch. I'm not testing which proc is best this ladder so I'll leave that to you guys) it isn't "amazing" but it adds tri-elemental damage for two of which you have -200 enemy resists (fire and cold) so it adds a largely noticeable amount of single target damage. The only problem with Kraken Stance is you forego Bear Stance which is more important mid-late game until you hit close to 50% physical damage resist with just Blessed Life. So if you have 50% dr already and want more damage Kraken Stance is pretty decent because Bear Stance Shields at that point outlives its use. Other modifiers like more flat fire/cold damage, %ar (for bosses) is also great but make sure you slowly craft your Crystal Swords cuz it will cost a lot of shrines to roll.
Start with one Crystal Sword then find another weapon and roll for modifiers that are better than the current one you have equipped because rolling Cata + Banish is already hard enough. Throw in Kraken and it's like rolling for the lottery.
edit: last thing is i would recommend using cold early to mid/late game because it's strictly more damage for uber bosses. lemures are x8 projectiles while bloodthorns hit x3 times. the damage difference early to mid-late is hands down in favor of cold. late game you can run fire which has items (Sacreds like Que-Hegan for example) that have more utility as fire and fire scales better late game in comparison to cold mostly because wave-clear is necessary.