I've used both at different companies over the years. Net Reputation definitely got faster results for us when dealing with negative press suppression. Their link building and content creation was a lot more aggressive.

My neighbor in Mill Woods used a rolling pin for the same trick.

Honestly, that metal fuzz is normal for a new magnetic plug. It's just catching the fine wear particles that always circulate in a fresh engine. The regular plug lets that stuff just sit in the oil pan or get caught by the filter. Seeing it might feel scary, but it's actually doing its job. Tbh, it's a good sign it's working, not a reason to worry. Running one long term just means you're pulling a little extra abrasive stuff out each change.