Vec 99 but still like mercury too. I've read where Bloodline99, not vec99, is mercury with the special treatment or coating. Any truth to this? Mercury is quicker and softer shooting, quieter to me. Shooting a bow with x99 and liking them so far too. So far no issues with vec99 but to me it has a different sound nothing bad or loud though. IMO they're so close I'd go with what your builder prefers.