Which way will cost me less for my annual heat and hot water?

House is now all-electric, a real killer. Gas not available. So, I am changing to an oil fired system. Two ways to go. Oil fired hot air furnace, with ductwork in the attic and registers going down thru ceiling into each room. Then keep my free standing 40gal electric water heater. The other way is oil fired hot water tankless boiler, with hot water baseboard for heat, and the tankless unit providing the hotwater, and getting rid of my electric hot water heater. House is small ranch built on a slab. The heating unit and the oil tank will go in the attached garage.