I would do diesel again
We have a Volvo MD6A (10 hp, 2 cyl) diesel (35 years old and still ticking - never been overhauled) in our Ariel. It only uses 1/3 gal per hour at full speed, so my 10 gal tank gives me about 150-180 mile range. More than I will ever need.
Pluses - pretty much bullet proof. Keep the fuel clean (!!!!!!!!) and it will run for ever. Almost nothing that can break.
Minuses - noisy, heavier, harder to get good mechanics
The last issue is the biggest one. When I was trying to resolve a problem, I ended up doing it all myself because I just couldn't find someone who knew more about diesels than me - and I was trying hard since I prefer sailing over engine repair.
Too Contagious (1966 Ariel #392)