Since they are pretty much matched and neither seem to have serious confo faults, you have to consider what you want to do with them. Are you looking for a pleasure or a performance horse? Are you wanting a trail or show prospect and for what discipline? I think you should consider that and then get the foal that best fits that discipline. For example, the buckskin would probably make a better WP, HUS, or jumper. And the dun would probably make a better performance horse; roping, barrels, cow work, etc. I say probably because you never can be sure.