Divine Favor is very suboptimal unless the extra 2.5 average damage is the difference between living and dead minions, or you're caught entirely in ranged combat in which case you can't Smite. You need to hit 4 times with that spell active to barely surpass a 1st-level Divine Smite. Against a single enemy, it's even worse than Searing Smite, and I have no love for that particular Smite spell.
Bless is a great effect but requires a use of an entire action. Which means unless you cast it either in anticipation of an obvious upcoming combat encounter, or you scouted it well, or you're taking your first turn of the encounter with all enemies more than 30 feet away from you, it's better to attack + cast a bonus-action spell (which Smite spells are).
Crusader's Mantle, again takes an action to activate so same issue as Bless there. And your party needs to hit 8 times with it to surpass a 3rd-level Divine Smite, so unless your party has a Fighter ready to Action Surge and/or especially a caster ready to pop Animate Objects, it's not going to be an efficient use of your 3rd-level slot.
Elemental Weapon, at least has the hit bonus going for it, but again, generally weaker than a 3rd-level Divine Smite for the same slot.
I guess what I'm trying to say is that the "longer benefits" are overrated, especially when you consider what the effect is, and often the action (as opposed to a bonus action) you have to spend to get that effect.
Wrathful Smite with its crippling frightening effect that forces an enemy to burn actions on Wisdom checks to end it, or Blinding Smite to deal just 4.5 less damage than a same-level Divine Smite while making the enemy unlikely to hit you and your party more likely to hit them, those are often much better uses of your spell slot and your action economy than the above-mentioned spells.