"So, if I want to use G55, when the box popping up wanting to know where to move to my work zero I would type in +3 for each axes.
Currently, I am using G30 to do this. Is there any advantage to using G55 instead of G30?"
G30 will move your axes to the position predermined by G30.1, but you will have to reset your axes to zero each time to get the G30 position to be at a new work zero.
If you preset a position in G55 to be at work zero, then all you would need to do is just change from G54 to G55 to have a different work zero position.
Using G55 lets you use the same gcode file at a different a work zero position with no other changes needed, and no requirement to remember to rezero your axes.
Either G30 or G55 can be used to do what you are asking about, if I understand correctly.