Got a 998c on my console and going to upgrade my finder on the bow........looking at three options

788 hd di....798hdsi....898si.......I know the last option is the best but money is factored in here....798hd but what i've read the 798 does a lot better with the transducer upgrade and with interference on the terrova trolling motors...didn't someone have a chart that showed what views each depthfinder would give you linked together?Give me some ideas...thanks