For Clerics, Turn Undead and Pelor's Radiance depend on what your chance to miss is, really. If the enemy is hard to hit, Turn Undead does more damage. If your enemy is easy to hit, Pelor's Radiance wins out. Does that make it worth a feat? That's up to you.
On the other hand, Pelor's Radiance is alright if you're a paladin who wants to do more to an undead than just your attacks.
But then, Paladins don't have troubles with undead. Radiant damage hurts undead hard.