To the best of my knowledge Medallion and Xuen sim very closely to each other in that case, so I would say it is up to personal preference which one you pick in addition to Lei Shen's. My personal opinion would be to go with Xuen since it stacks better with reck during opening and execute bursts (additional crit buffs during reck are pretty much wasted). If you haven't bought the Medallion yet, the VP could probably be spent better elsewhere.