I picked up a good thread over at www.24hourcampfire.com,
fellow named Ken Howell in the 'Ask the Gunwriters' forum had a long thread about how it is pressure and temperature over time that cause throat erosion. Since the time the bullet is in the barrel is somewhat constant between the different powders, the only thing left is peak pressure which is related to temperature, the higher the temp the more metal is eroded. As I understand the peak temp is above the melting point of the barrel metal, but it occurs so fast that there is little time to melt (erode) the barrel.
What was really interesting in the thread is that he goes on to logically talk about how his preferred pressure he loads to is around 50,000 psi, rather than the 60k psi at the SAAMI max.
So back to the powder issue .. I would imagine that loading for accuracy over velocity is the appropriate method, though are we talking about splitting hairs or is there a big difference.