I would definitely default to playing the PF at PF and the C at C. Most PFs are still sufficiently interior-focused scorers, if they're scorers at all, that there isn't a huge inherent advantage to having higher shot blocking at the 5 vs. the 4. I'd rather have the guy with better ball skills at the 4. With that being said, neither of them is a particularly impressive scorer, so it doesn't matter a ton. I'm with TJ, I'd tend to rotate the stronger defender onto the more dangerous scorer on my opponent's team.