I have installed both, the Lowrance on a friends boat. I was shocked at the size of the transducer. I think it produces a weaker signal and needs a larger "antenna" to pick up that signal. I am sure I would destroy it with a stump if it were on my boat.
The signal works by "line of sight" so if the signal is being shot to the left and the foot of the motor is blocking it, you will have a blind spot. This is where a jack plate helps. I dont have one so even with the shorter transducer of the Humminbird I still have to trim up a bit to shoot the left side on Side Image.