Delk was an amazing player. Did a lot of other things really, really well, nit just shoot. Had amazing basketball IQ and with those arms (and with no neck) he played about 18 inches taller than he was listed, which made him a really deadly guard. He was quite consistent with his outside shooting, but the real reason the legend grew up around his shot was his range. He hardly shot any worse from half court than he shot from just outside the line.
But Lamb shot a higher percentage from 3. The only way around that is use onky Delk's senior year against Lamb's fresh & sophomore years. And even then you would have to overlook the fact that Delk's percentage was higher his senior year simply because the '96 team had too many threats for opponents to key on him. You would also have to overlook the fact that Delk's 3 point line was a foot closer in than Lamb's was. No real contest between the two as far as 3 point percentage, though Delk is still the better overall player.
Booker's pair of slumps has kind of elimated him for now. Obviously if he can come back and play a whole season as his better-shooting self he'll be a serious contender.