While it may take a brief moment for you to resume attacking with your quick move, blizzard much better than ice beam. The damage, whether it feels like it, is superior to ice beam. If, perhaps, you personally are suffering from some type of "delay" bug, it is likely that others are suffering from the same and it will eventually be fixed. Thus, I wouldn't base my decision on that.
As for a 100% IV Lapris with Ice Shard and Ice Beam, unfortunately, such a Lapris is not a wise choice to power up. While IVs are important, a pokemon's move set is far more important than the IVs.
Good luck, Buddy!