In your opinion, which primary stat is the best?

What does the initial characteristic mean? The one that will be upgraded after the first level gained? It won't make much of a difference, so you can't say that it will be better as an initial characteristic... The second level might upgrade the same characteristic again, but it's unlikely. The third level will definitely upgrade a different characteristic, and after that, there will be upgrades to various characteristics, depending on the chosen race. By the time the characteristic has been upgraded several times, the hero will be around level 8... I don't think such a hero can be called an "initial" hero. (I'm sure he won't have characteristics like 1, 1, 8, 1). So, I just don't quite understand how the question is posed.
P.S. I voted for magic myself.