My opinion is that both searing and thunderous smite are good enough spells, with some exceptional situational uses. As for wrathful smite, I think it is a very strong 1st level spell. It is kind of the equivalent of bane for a different battle. While bane can debuff up to three creatures, wrathful smite can really really debuff one creature (save it for a very strong creature). Granted, a strong enemy might have a good save ,(might), but if he fails it, then it's game over. Encounter won. Encounter made much more easy to be fair. Plus, it is a first level spell so you can spam it until it works, if you feel that the enemy has a decent chance of failing his wis save.