You should probably have both?
A surge protector prevents a line blowout or lightening strike from frying everything downstream connected to it (on your end of the lightening strike or blowout).
A GFCI (ground fault circuit interrupter) will trip if there is any stray current between your electrical mains and the ground. What this does is that if a wire gets severed in your tank, or a pump starts heavily leaking electricity, this will actually catch the electricity going into the ground plug from something else in the circuit, and will turn itself off (and presumably everything upstream of it). It's like an auto-off switch for a dangerous upstream leaking of electricity.
It's not the same as a grounding probe, but it will use the default grounding from something in your tank (your main pump, a skimmer pump, lights, etc) and when there is a connection between the main AC plugs (standard left right plugs on a plug) and that ground somewhere in your system, it turns off, potentially saving your life and your tank as well.
Worth noting that GFCIs get old and start to falsely fail. You should buy a replacement or two and test the line before going and replacing pumps.