I think it depends on the size of your powder room. If it's newer and meets ADA requirements, it's fairly large, then a cabinet can look great, especially with a marble top. But if it's small generally a pedestal sink looks better because it gives the feeling of more room. That said, I once did a powder room in a former under-stairs closet and put a tiny cabinet that went from wall to wall with a teeny tiny sink and I loved how it turned out! Also gave a tiny bit of storage.