I think that it's a pretty close call between the two.
For rooms I'd probably go with the Rosewood as it's newer and has a really nice design and the suites look amazing, but I'm not familiar with their service levels and the Langham really is top drawer in that regard.
Incidentally, Scarfes may have won top Europe bar design, but the Artesian which is the Langham bar has been #1 in the Top 50 Bars of the world for the last 2 years and just won Best International Bar in New Orleans a couple of weeks ago
