I have both on my boat. I have LVS34 with a forward/down/perspective mount, and Mega 360.
Let me start by saying - I am not a fan of Humminbird imaging/graphs/etc.
However, Mega 360 is much better than LVS34 Perspective. I find Perspective largely useless. It very much depends on the depth of the water.
While I agree with the above post that Perspective has the advantage of being real time... the quality of the image and range is often so poor that you can't do much with it.