Definitely going to open a can of worms with that question. Many opinions and everybody's setup is going to be a little different but I'm happy with my Lowrance units. This shot was taken with my HDS9 on the bow using an HDI transducer.
As you can see I was in about 7 feet of water and moving slow. You can see the crappie in the stakes showing up as bright white dots. They were tasty.