I have it narrowed down to these two Lowrance units. The first is gray scale and has both a gps/chartplotter and a fishfinder. The second is a fishfinder only but has downscan imaging. They are both $199. What do you think. This will be for my trolling motor.

Lowrance® Mark-4 Fishfinder/Chartplotter | Bass Pro Shops

or

Lowrance® Elite-4x DSI Color Imaging Fishfinder | Bass Pro Shops

Thanks