The lower heating value in BTU per pound fuel divided by the recommended stoichiometric ratio by weight gives an idea about the heat available in a pound of fuel air mix. The Standard 110 octane leaded gas has this: 18,700 / 15.0 = 1,247 BTU per pound air fuel mix.
The SS100 104 octane unleaded has 18,000 / 14.2 = 1,268
The 260 GT Plus 104 octane unleaded has 17,400 / 13.7 = 1,270
The leaded gas is more efficient. It has a leaner stoichio ratio. It also costs a lot less. The unleaded gases have the potential to make as much or a bit more power.
Octane needs are a big unknown factor. The piston crowns, exhaust ports, valve heads, and combustion chamber will be ceramic coated. I am not sure if this will retain heat and require more octane than an uncoated engine.