2D sonar or Down imaging

[guimaras]

Good day Ladies and Gents,

I just would like to seek advice about fishfinders. I am currently outfitting my small inflatable fishing boat with some electronics. I have the option to install either a 2D sonar OR Down imaging for it. I usually fish estuary, inshore and coastal on a good day, with depths from 2m to 40m. I know some units can show both but the choices I am given does not include those. If you were to choose just one...would it be 2D sonar, or Down imaging?and why? Which one would be more useful?

Cheers for the help.