If you only have one display and want 360, you have to get a Side Imaging unit.
IF you are going to get two displays, one has to be a Side Imaging unit and the other can be a regular 2D unit or a Down Imaging unit then both can display the 360 view.
The 360 is not a traditional plug in transducer, it is an Ethernet accessory. Traditional transducers plug directly into the display's transducer port.
There are two styles of 360 transducers. One is a transom mount and looks like the Talon shallow water anchor.
It has a deploy system to lower the transducer to below the hull bottom.
The other is the bow model that clamps to the upper shaft of a cable steer trolling motor (designed for the Minnkota motor) but can be adapted to a Motor Guide cable steer trolling motor--I have that setup.
Humminbird introduced a whole new model line for the 2014 model year. Check their web site.
No Lowrance does not have anything like 360, they are trying with their Spotlight transducer, but it is not well received since it does not scan on its own like the 360 does. You have to do the scanning by turning the trolling motor (cable steer type) which seems to be a challenge to get a usable image.
You would have three learning curves to overcome. Traditional 2D sonar, Side/Down Imaging, and the 360. You have to commit yourself to put in the time to learn them if you ever want to enjoy the benefits.
Look at the posted images at the top of this topic to see what the deal is.