Adding milk first increases the volume to heat and lowers average temerature, but adding it afterwards seems to have similar effects. How can you compare the two?
By adding milk first you reduce heat loss during heating due to lower average temperature. The rate of heat transfer to the surroundings depends on the difference in temperature between the object and its surroundings, so lower average temperature-> less energy lost to the surroundings.
So if you add milk first, you will get higher temperature at the end.
But personally, I prefer to add milk after, as it's more sensetive to overheating. You can heat cofee to 100C without any damage to it.
You may think that I am making fun, but it is not so. The experimental way, when available, is the best solution. You have a courious mind, dont stop. A personnal learning process is good.
end of recipe ;-)