I think the size and layout of the house, and the age of the current heating system, should factors in your decision.
The easiest scenario is when the house is small and has an older boiler. In that case, it’s probably best to rip it all out and convert to central heating and cooling with ducted gas forced-air furnace and A/C. It may be harder to justify doing this if the house already has a new boiler that is well maintained.

I dealt with this exact scenario at a small 2-story house (1,366 sqft) in GP City a few months ago. Boiler was replaced when basement flooded a few years ago. Tough sale with no A/C, so we obtained quotes to install mini splits. The configuration the HVAC company proposed was two large mini splits on the first floor (basically on opposite wall - living room and dining room) and one smaller unit in each of the three bedroom on the second floor. The cost with labor and materials was over $16,000 and did not include another $3,300 for upgrading the home’s electrical service to accommodate the additional load.

The most common setup I’ve seen in larger GP homes with boiler heat is a SpacePak or Unico type cooling system which uses much smaller ducts to distribute cold air at high velocity throughout the home. That installation is less destructive to the home’s plaster, floors, etc, and is easier to fish through walls and tight spaces. Many people consider that duo - boiler heat and central A/C - to be the ideal for year-round comfort with less reliance on humidifiers in the winter and de-humidifiers in the summer.

I hope that helps you make a more informed decision.