I would go with the Lowrance or Garmin. I bought the Hummingbird 999ci hd with sidescan, navionics etc. a few months ago. Starting to get used to it and getting dialed in but liked my old Garmin and thinking about going back to a newer one. The side scan images are pretty neat for structure on the bottom but don't show you much near the top of the water column and not sure it's much use in our waters. If you decide to go Hummingbird and want one that's only a few months old, I'll work you a deal.
in the past 3-4 yrs I have bought Hummingbird 789 (SI/DI) - Lowrance elite 7 (DI)-- and just got a Garmin 9" with SI and DI (forgot model)
The Garmin interface is easiest to use ,transducer is the size of ft long hotdog and it sometimes makes it hard not to pick up some motor interference on the side scan.
the Hummingbird -- I had to keep book in boat, to remember how to get to some features..
Had no issues with the Lowrance .