Personaly, I think it's all in peace of mind. If you replace your grounds, and have some electrical problems years from now, you can most likely rule out ground issues, at least with the battery and engine. I upgraded 2 of mine, to 4 gauge wire and some strong mounting brackets. I don't really remember noticing a single improvement, but at least I know they are strong and new.

 

The ground wire is just one of the wires in your car. Unless you upgrade every single wire you will not notice any difference....and probably not even then. It's just hype to part you from your money.

I have a friend that works at a high-end audio/visual store. He sells lots of $150+ power strips with heavy wires and gold contacts. He neglects to tell the buyersthat they won't see/hear any difference because the wiring inthe walls getting to the extension cord is still the same-old same-old.