The issue with 410 out of a handgun is the lack of velocity behind all that potentially useful buckshot. Buckshot's light weight means that if you take enough heat off it, it can start to fail, and you might be throwing large numbers of less than effective projectiles. I've never said for sure that the 410 handgun is without merit, but criticism's of it certainly do have merit as well.

As for the discs, I'd say they are completely and utterly in every single way inferior to round ball in reality. Ball and buckshot are virtually even, meaning they resist tumbling and even if they tumble in terminal performance, they are guaranteed to crush nearly identical cavities every time; the short flat disc runs the risk of flipping and presenting a least surface of resistance crush path which can actually minimize its effectiveness, i.e. you shoot a quarter at someone expecting it to crush a quarter size crush cavity but instead it flips sideways and instead cuts a disc path through that does very poor damage, and very little cavitation.

tl;dr Ball and long conical resist flipping at best in terminal ballistics, or in many cases can take advantage of it, whilst the short conical disk is at high risk of being flipped from its most destructive trajectory and face to the least. We don't even have to get into the lack of weight, and obviously it not only suffers from lack of sectional density but also stability.

If you are going to shoot 410 for multiple projectiles, 000 buckshot would appear to be the choice, and copper discs are a very poor choice.