as far as being more productive finding fish, put it on the transom, unless you fish some real small lakes then id put it on the trolling motor. the reason being you can cover a lot of water running 2d and mark fish schools as you go. then you can come back with cv or sv to verify fish, cover and structure. throw out a marker bouy and go to fishing. if you have a console or a place to mount where you can flip the mfd around so you can see it from front and back of the boat, even better. ram mounts are awesome for that. you just have to keep in mind the distance from the mfd and transducer and adjust your boat accordingly.
if you fish real small lakes, no wake lakes, or if you do a lot of vertical jigging then put it on the trolling motor, but keep in mind you have to keep the tm in a straight line for good sv images. if it moves then the image will smear. like ruger said wire tie the crap out of the xducer cable to the tm shaft. another good $60 investment is a transducer saver mount. beats having to buy another $350 xducer when you smash the tm into the rocks. also dont pull power from the trolling motor battery or wire tie the xducer cables to the tm cables. you will pick up too much interference for the mfd to be usable when you turn on the tm.