Side scan and downs scan definitely have their place in a boat. Expect the technology to improve and the depths you can get clearer target returns to increases as manufacturers fiddle with different frequencies.
I have 5 transducers in my boat---in the picture above, the yellow "wet box" is an in-hull M260 (a 1 Kw 50/200 KHz that shoots through the hull) . The big brass thru-hull is an Airmar B175W "Chirp" and the P79 behind it is an in-hull for just depth readings
But my favorite transducer is the tried-and-true P66 ( 600 W---50/200 KHz) ---that one is on my transom. Many people would agree that with a P66 transom puck, a Pacific Northwest salmon fishermen really doesn't need any other piece of sonar/fishfinder technology. That has been my experience also, but as I kicked my cocaine habit years ago I just had to, no doubt just had to, replace it with another habit....now I have this irresistible compulsion to stick my face into large MFD screens that show interesting painted pictures of target returns...which explains all the other transducers...