The Helix 9 will have a smaller display and different width to height ratio
16:9 like the Helix 7. The 1100 series has a 4:3 ratio.
The Helix 9 has a higher pixel density display by about 3,000 per square inch.
The Helix 9 has Auto Chart Live if you want to do contour mapping in real time.
To upgrade to the HDSI transducer from the Compact SI that is included with the Helix 9 SI GPS, it is about $85 including shipping. Then add the cost of shipping the Compact SI back to Humminbird.
The Helix 9 series replaced the 800 series, the Helix 10 series replaced the 900 series, and the Helix 12 CHIRP series replaced the 1100 series.
In each case the display size was increased by about 2" diagonally.
Edited by Wayne P. (06/14/16 03:28 PM)
Humminbird Helix 12 SI, 1198c SI, 1198c SI, ONIX 10 SI NT, 360, RC-1