Gps combo finders?

Does anyone have any experience with the following fishfinders:

Humminbird HELIX 8

or

Garmin Striker 4

I use two different kayaks. I like the idea of a unit that is all in one and can be clamped to the side of the kayak. Most of my fishing is in less than 40ft of water.

I was a wonder:
1 - Are they any good?
2 - Do they have decent battery life?
3 - What is the difference between down imaging and dual? I don’t have any fishfinder experience.

Thanks.

I think you may get more response in the Boating or Marine Electronics forums on https://www.thehulltruth.com/