Performance is relative. All of those 15s will push that dinghy
loaded pretty well. The 2 strokes are lighter and cheaper but not sold
in many places these days. At some point in the not too distant future they will not be available at all new. The 4 strokes have better fuel
economy, less emissions and are generally a more modern, efficient smoother running engine
, also quieter. No mixing or gummed up carburettor.
As said, I lean towards the 4 strokes with EFI.
Those who are used to the 2 strokes will stay with them as long as possible.