Hi,
Diesel-electric ? Good.
1. As tri-star mentioned, the first "engine on water" application was electric. If I'm not mistaken, Saint - Petersburg, Russia. Early in 1900s ? That boat could make appx. 2 knts... DC current was used, provided by batteries...
Good sides, basicaly:
1. Diesel engine(s) can be placed, whereever You like and how do You like.
2. No reduction gears needed. Even if You have multiple engines / 1 propeller.
3. As usual, (but not always), with such installations diesel engine runs at constant RPM, what is very good for it.
4. No steering gears needed, if AZIPOT / AZIMUTH systems are in use.
5. Smooth control over propulsion, I think one of the best.
6. Total weight of propulsion unit will be less.
Not so good sides, basicaly:
1. They say, "too complicated". This will depend on developer / manufacturer. You know.. inverters, converters, again inverters...
2. Possibility of very strong electr. / magnetical fields.
3. Depends on a power, probably highly-experienced personnel will be needed to maintain whole thing.
Not usual marine engineers.Trained electrical engineer will be "in charge"...
So, that was my point of view.
Hope, this info will be useful for You.
P.S. I worked on ice-breaker, that ship was diesel-electric, 12000 kW. There are 4 main diesel generators AC, 4 propulsion DC el. motors., 4 converters.
So, I remember, that 1 m-thick ice was not a problem...
rgds,
Andrei