Lots of pros and cons to consider.
First, an outboard solution is less-expensive... the outboard version of the Aloha will cost less (but fetch less when you sell). If / when you need repair work, an outboard again will cost less... substantially less. Though some might counter it would need more frequent repair.
If your outboard crapped out, you could source a used replacement on Ebay or Craigslist and be back in business in days... I scored a used 15 HP 2-stroke for $600, tuned it and replaced the impeller at home, then installed it in under an hour; I was out of service less than a week. If your diesel crapped out, you're probably talking several weeks (you could lose 1/3 or 1/2 a season in Ontario).
The other knock on outboards is that they can lift out in a rough, pitching sea. While true for stern-hung outboards, it may not be valid when the boat has a purpose-built outboard well in the stern. My 28-footer has a purpose-built well, and with my long-shaft 15HP outboard, I submit my prop is just as deep as an inboard design's prop would be. I have a remote throttle & shifter and electric start so the operating convenience is the equal of an inboard. And with a slot cut in my transom, I can raise my prop out of the water when sailing (no drag) or on the mooring (no fouling).
Yes, an outboard runs on gas... much more volatile than diesel fuel. 4 stroke outboards are quiet and reasonably efficient... 2 strokes not so much. But diesels are louder than either.
Your 27' boat may be in the same league as my 28 footer; it is getting to the point where older boats of this size are not very attractive on the resale market... if you had to replace the diesel it would require you to invest around half the boat's entire value.
In my opinion, in boats of older vintage in the 27-28' size range, I'd always opt for the less costly, simpler design solution... that which gets me on the water while minimizing my spend on a boat that won't fetch much at resale time.
