I fished with a humminbird 385 ci for years and still use if as my backup. It is the pre-cursar to the helix series. I have caught lots of fish with that unit. In my opinion the helix would do both soft and hard water very well for you. They are very versatile units
The 2 reasons i bought a vex was i could see a fish right on the bottom better, and the interference rejection was better when fishing in large crowds.
My buddy has a helix 7 and we fished a lake with a very dirty water column sitting side by side last year and he was able to see better then me with a flx-28. For some reason that night i struggled with that lake.
If you want both hard and soft water capabilities i would go with a helix.