Fish Finder opinion

I've been researching fish finders and had my mind set on the Humminbird 565 when I stumbled upon the portable Hummingbird PiranhaMax 215.

I'm looking at spending up to $200.

Are those portable fish finders worth anything? Are they a hassle?

Or should I just buy one that requires installation?

What other material (cables,..etc.) would I have to purchase to install it in my boat? Or would the package come with everything I need to install it (like if I bought it from Cabelas). Is it hard and time consuming to install? Should I do it myself or bring it to a shop to get set up?