Im sure this has been asked 150 times already but i looked through 10+ pages in this subforum and didnt see anything.
Is there any advantage to running the anti vibration pads under the motors? I mean, i understand the concept but is it just adding weight or does it actually help?

I have them on my 5" (photos HERE), but the filtering in Betaflight is so good these days you don't really need them. I only stuck them on because it was my first build using a much older version of Betaflight and I wanted to take a belt & braces approach so I didn't have to mess with any tuning. I don't think I would bother these days on a new build.

Out of habit really. It's actually one of the first things I print out when I start a new build. Like Snow said it probably does not do much given today's filtering but man I'll take every bit I can get lol.

Well for the price of them i guess it cant hurt to try lol

One thing to keep in mind with the anti-vibration pads is that you will either have to use some loctite on your motor screws, or you will need to periodically keep checking and re-tightening them because the screws will start to vibrate loose over time. If you do up the screws so tight that they don't need re-tightening every so often then it means you've squashed the anti-vibration pad so flat that it's not doing it's job any more so is pointless. I use the re-tightening option because loctite can sometimes make it a PITA to get the screws back out again when you actually have a reason to remove a motor.