I always asked the same question and always got the same answers. Match it to your fishing. This is what I did I started off by looking at the waters I fish, now I go from shallows all the way to about 150 feet, I fish all trout kokanee and sometimes some gills and perch in local ponds. So now I ha to figure out what would work for me an really any of them would work, I ended up choosing vexilar, they have been in business for so long that I figured couldn't go wrong. My dad talked about the guys that always had them so I started researching them. YouTube is a great source, I would look at product reviews, how to's, and people using them. I ended up fishing without anything but a little fishin buddy finder for years this year I got one for Xmas. I got the fl-12 if it was my choice I wanted at least the fl-18 with the auto zoom but iv used mine in water that was 10 feet and out to 40 feet. I love it, once I used it or a full day and started learning all the functions an starte seeing fish it was a game changer. My brothers were stealing it outa my hole to check theirs. When I'm in my shack I can drill 4 holes in a square around 6 ft apart and faintly see my jig as well as the 3 jigs in the other holes. I want to buy the transducer that has the 2 different degrees in it for different fishing types. My brother purchased the Marcum 5.6 showdown but has not received it yet. I'm sticking with vexilar but my suggestion is find what you want an if you got the money jus learning how to use it is a big thing. If not buy a less powered one or older model and you can always work up.