I have an RT178 with a 75 Merc 4 stroke. We had a ranger R61 before. There is not as much storage room in the RT178 as there was in the R61. That is one drawback. As far as running it is great.
We (my wife and me) really like it. We tried a used RT188 with a Evinrude 115 hp motor and liked it real well except when running diagnostics on the motor it had had problems.
Make sure that there is ample room for all your gear especially your fishing poles. It should run about 40mph. Look on Youtube for some videos that might help you decide.