Humminbird Helix 9 Chirp SI. HD or stock transducer?

I have the stock transducer. Who has switched to the High definition transducer, and what is your impression? Worth the $$? Thanks.

The Helix 9 CHIRP model is the MEGA SI and comes with the top of the line MEGA SI transducer. Why would you want to degrade the unit's performance with a lesser transducer?

If you had the first generation Helix 9 SI GPS, then you could improve its performance by using the HDSI transducer.