You are aware that you don't have to choose between smite spells and divine smite? If you have set divine smites to "ask" then every time you hit a target with a smite spell you will be asked if you want to add a divine smite on top.
The issue becomes that smite spells cost a standard and bonus action. Meaning it would be more beneficial to simply utilize both actions for normal attacks allowing you to add Divine Smite to both attacks.
Given the plethora of ways to attack with a bonus action (Dual wielding, Polearm Master, Great Weapon Master and Duelist's Prerogative) it becomes exceedingly less worth it to use smite spells if damage is your main concern.
With the sole exception being maybe Searing Smite because of it's potential 10d6 of burn damage.
This is further exacerbated if you care about maximizing spell slot usage so only smite on a crit, whereby not only does normal attacking save you the cost of the smite spell, but also means your bonus action attack is an additional crit potential.
