Hey Al, no sounder puts you onto fish they just help interperate whats on under the water. most sounders these days are of a very high quality and will help you do this.
As for the side scan sounders i cant comment on the humminbird units as i havent had much to do with them. I have recently added the structure scan to my hds units and it makes so much difference. you cover so much ground while sounding it not funny. with the incorparated down scan i find there is not much that cant be found in the area your sounding. i can not speak highly enough of it. The readings between hard bottom, trees or other structures and bait is well defined and easy to distinguish.
My only advice with the lowrance ss is to buy the biggest screen you can afford. the bigger the screen the more detail you are going to be able to pick up. in saying that i have 2 7in units and a 5in unit and you can still get good readings even on the hds5.
Hope this helps in some way but you deffinatly wont be dissapointed in the lowrance product i wouldnt want to go fissing without mine anymore.
Cheers Whytey