So I recommend taking one level in each first. This way you gain partial bonuses from both as they are intertwined nicely. Then bump PS to 2. I say PS first because it will make every hit more capable of producing a crit hit, while MC will only affect hits that are already critical. Increase your odds over increasing damage that may happen rarely.
From there, it will be more based in your level (if you are 2+ most enemies, chance to insta kill is nice) and weapon of choice (faster weapons, more hits, PS more important). At 12 points to max both, you've got 6 levels to gain to see what works better.
From other topics, I'm assuming this cleric will not join the WG, so that takes Duel off the table. However, once you have your cleric guild Cleric built up nicely for future content, start another cleric you will put in the WG. Retribution and the other adv. cleric skill available pale in comparison to Duel and Heavy Hand for current content. My 2nd cleric in the WG is a wrecking machine that rarely has to head to an inn.