I wouldn't label these maintenance issues as Inboard vs. Outboard. I'd tend to think of them more as Used Engine vs. New Engine type issues. As any engine ages, depending upon the level of care given to it, it's going to start to experience component failures. These engines live in harsh, damp environments and corrosion tends to hit the electronics and wiring very hard. A used OB can cause you just as much grief as they age.
One advantage OB's have with items like alternators, starters, ignition coils etc is that they tend to be well sealed from the elements inside a water-tight housing which can prolong their life. Yet, these components can and do fail over time. The advantage of most I/O's is that replacing these components can be done by most guys who are willing to read and can turn a wrench and the parts are a fraction of the cost and can be purchased from many sources. OB parts are proprietary, expensive, and often require specialized tools for replacement as these engines are assembled like a jig-saw puzzle.
If you dropped in any new package -- either a new OB or new I/O I suspect you'd be happy for many years. A pod with a new OB would be fantastic assuming you LOVE your boat and intend to keep it. Dropping in a new modern 3L with EFI and the like would be a fraction of the cost. Yet the cheapest thing (very likely) is to simply fix what you have.
