Hello!
I would say that between 10 and 15deg of headstock angle there won’t be any tonal difference. But as Anthony pointed out, with a different break-up angle you will change the orthogonal force exerted on the nut, therefore :
– the feeling of the string stiffness
– the smoothness of tuning
– the tendency to rub&buzz on the fret slots
I never made a direct comparison or an experimental check of this parameter, to assess the actual difference and impact. I use a 14deg angle on acoustic guitars, little less for classical one, and I am satisfied with the results. I cannot see how one could use this parameter to tweak the performances of a guitar, but I can be wrong on this one…
Cheers,
Giuliano