I use a Butterfly display with SYM and find they are complimentary rather than redundant. Each provides the information in slightly different form. The Butterfly is better at tracking the closest target and giving climb rates. SYM gives me the big picture of all the ships around me and at greater distance for situational awareness.

I prefer the Butterfly warning for collision over the SYM verbal warnings. At high speed it is difficult to hear the SYM warnings and respond without needing to pull your view back in the cockpit and read them.