It all depends on your targets and how quickly you want to get there.

IF your target is silver streaks, sterling pastels etc etc then pewter x pewter is the way forward.

If however your goals are pastel pieds, black pastel pieds, pewter pieds and panda pieds then there's only one pairing to go for.

Don't forget the easiest answer to this question is your pewter male will quite happily visit both your pied and pewter females come the right time of year!!

Personally, out of the two, I would be much more excited about the longer-term pied project. Trust me when I say there is nothing more satisfying than that Loooooooong term project producing results, equally there's nothing worse than waiting for it to happen and waiting for things to grow on!! The joys of royal python breeding!