Sulthraze is a more safe choice due to the fact that it adds a dot, good against runners and stealth classes, it has instant burst dmg on initial hit which is good in pvp (especially makes it harder for healers to predict healing required on themselves as well as their teammates). And another important factor is that it has baseline stats which are quite strong too. As a paladin though, your str>ap>sp(spellpower) so your heals will also be bigger the more strength you have. So imagine getting that str proc on destiny, and your flash heal will probably top you off completely which also can make it very handy, but again it has 0 stats and is only useful in its RNG time. I would probably switch between them depending on the encounter and situation. If you feel like you don't need more survivability I could go for destiny. But if you do, then sulthraz is definitely more defensive also, due to the extra stam/vers but also that the proc actually lowers the dmg done by the target by a not so insignificant amount at this level.
A weapon I would also consider if I were you/a retri paladin, is the Baron Rivendare's Sword. It is most beneficial for a retri paladin of all the classes that can use it because the health regeneration scales with spellpower and only a retripaladin has spellpower who can wear a two-handed sword.
I've seen it giving about 500health every 5sec on 59/60 retri paladin twinks which is nothing to laugh at especially when teamed up with Blessing of Kings, giving you around that 1k ekstra damage mitigation every 5seconds making you pretty hard to kill!
So to sum things up.
- For full burst/dps/with a pocket heal go Destiny.
- For more balanced setup with both dmg and defense go with Sulthraz.
- For a full turtle setup go with Rivendare's Sword.
This is just my opinion. I don't have a lvl 59 retribution paladin, so take it with a grain of salt.