How much difference do lower mass cartridge clips make in playback?

Copper clips are unlikely to be pure copper. Also especially silver clips are very unlikely to be pure silver, because both of these metals would be a poor choice for maintaining a tight grip on the cartridge pins. Most cartridge clips are problematic, but their weight or mass makes such a trivial difference that I have never even thought about this as a problem. Why do you bring it up?

I have one clip that's lost it''s retention (I believe it's partially broken) and was inquiring as I consider replacing one or all.

I can suppose no reason why a "low mass" clip would improve sound (rather the opposite).I like the Mitchell clips better than the Cardas. See if you can stick a round toothpick in the loose clip and squeeze carefully with small pliers to regain tension.

I did that several times, hence I believe it's broken.

Thanks to all who responded. I have some JA Mitchell silvers’ on a wire loom I made for my ET 2.5 years ago. I may remove them and replace to my 3d arm. Years ago, in searching for the shortest length clips I ran across the Clearaudio clips. I bought them purposefully to use with my Acutex 420 STR on my tt project, as the pins protrude at a steep upward angle making the normal length clips impossible to use and feel good about it.