An angle clamp can be used to do the same job as a weld clamp magnet but a weld clamp magnet is much easier to use.Angle clamps require you to place the metal into the clamp and then tighten the clamp until you believe it is tight enough. This will take time and effort to do so correctly.
Weld clamp magnets on the other hand only require you to place the metal onto the magnets to hold it tightly and in the correct position. This means that there is less time and effort involved.
Angle clamps have to be attached to a work surface in order to use them in place effectively. Weld clamp magnets can be used anywhere as they only require their magnetic force to hold metal in place.