Depends on a persons style of fishing. I have both a terrova and a fortrex. For my style of fishing I keep the fortrex on the front of the boat. Don't anchor unless I absolutely have to. The Fortrex, with its cable drive, has an immediate response to allow me to pretty much go handless all day. I also have one of those minnkota quick release plates on each trolling motor if I want to change them out. The Terrrova does have its advantages but for fishing over structure or a school of fish hard to beat the Fortrex.
Now to your main question...what good is a depth finder going to do a person if he can't troll up to the spot (or stay on the spot) if he doesn't have a trolling motor. Anchor???? Been there done that...at the MOST I will have one anchor down and use the trolling motor to keep me close to the buoy or spot your wanting to fish. Before I had a depth finder on the bow we could at least throw out a marker as a way point so we know where we were located in relationship to the structure or fish. Using the trolling motor you have some room to work with. Very easy to be off 5-10 ft without a waypoint or marker of some sort. That can be costly when it comes to crappie fishing.
Sacred Heart of Mary, pray for us now, and at the hour of our death. AMEN
For those who believe, no explanation is necessary....for those who don't, no explanation is possible
For the sake of his sorrowful Passion, have mercy on us and the whole world