You could try to analyze each ball separately using the projectile motion equations, but that would be more difficult than applying conservation of energy ideas. Try the master energy equation:

U_i + K_i + W_nc = U_f + K_f

Neglect air resistance, so W_nc = 0. The equation becomes:

U_i + K_i = U_f + K_f

The initial and final potential energies are the same for each ball, because they all start from the same height and end at the same lower height at ground level. They all have the same initial kinetic energies...so, they all must have the same final kinetic energies.

Therefore, each ball hits the ground with the same speed.

Note that it doesn't matter what the initial angle of the ball is. That affects the direction of the velocity each ball has on impact, but not the magnitude (i.e., the speed).