Does the hummingbird green thing sink or float?Are you looking for something to use on a boat / kayak or something to use when shore fishing?
The lowrance is way more advanced than the smartcast unit and designed to attach to a boat or kayak hull. The smartcast is basic (I have one, an RF20) and can be used cast and retrieve with a rod and line from shore. I dont really use it as a fishfinder, but it has been really useful for mapping out bottom structure and depth where I fish.
The green transponder floats.
I did a short write up on it here.....
http://fishontoronto...onar-fishfinder
You can fish bait off the bottom of it, but thats not for me....
I generally use it when I am scoping out new or existing spots for depth and structure. I mostly fish around downtown where the water is either deep or dark, or both. You have to be realistic as to what useful info you can get from using these low end units for less than 100 bucks.