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

I could imagine that the less flexible, stiffer headshell wires may vibrate more than Litz types. Likewise, slightly loose clips may resonate causing distortion. I’d like to try a single strand of pure silver wire wrapped in silk. Better construction -even if slighty heavier- should give you a better result.

Gold and silver are to soft for clips. That is why the most are made
from gold -or silver plated bronze. Clearaudio's are machined from
Rhodium and than gold-platted. All headshell wire are isolated 
so hardly resonate. 

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.