Blue
Ravenous Bugblatter Beast of Traal
My experience, with a party where a dwarf paladin is doing a lot of the heavy lifting, is that smite often lets the paladin deal a lot of damage quickly in early fights, which then means that by the later fights the casters still have a lot of juice left in their tanks while the paladin's is running low.
I've almost never seen the PC in question use the Smite spells, however. To me, that suggests that the Smite ability is overpowered compared to those spells. Then again, the paladin in question has the oath of Vengeance which gives him hunter's mark which he'd have to drop in order to use those, so the situation might be different with other paladin types.
Heck, I've often used Smite spells and Divine Smite when I wanted to deal out damage quick.
But really, for low level slots the damage bonus of that extra die makes Divine Smite the better damage dealer. Both (a) most play happens 1-10 and (b) focus firing to inflict the "dead" condition are helped by this, we often see the damage as more worthwhile.
But the riders on some of the smite spells are fantastic. If you're overwhelmed as tank and you fear someone off, grat. Or off dealing with someone by yourself and the damage difference between a Smite spell and a Divine Smite isn't going to drop them this round but a condition can sure make you a happier camper - those are when the Smite spells are worth it. I unfortunately see players get into the rut of just using Divine Smite and they don't use the Smite spells at times when there would be a big advantage from doing so.