ONIX is way more customizable ...and in that customization = more complicated menus ...

HELIX is dependable ...and much easier to navigate thru the menus ...

If you like more customization, pushing buttons and changing settings a lot = choose ONIX ...

If you like to turn the unit on and just go fishing = choose HELIX ...

Rickie

P.S ... and as Gene mentions ... ONIX (and ION) is the only HB that has 2d / dedicated DI / and SI in the same xducer ...