I have stayed at Langham twice and Pen once. Overall for me, the Langham probably wins on room hard product although there are tradeoffs in both.

The Langham bathroom finishes look slightly dated in terms of color and material, but the Pen's bathrooms are like 10+ years more dated and weren't as high end to begin with. See the difference in the shower, for example:

Langham:


Pen:


That being said, the Pen wins on pure function for the closet area and bathroom separation. The Langham bathroom has that shower window into the bedroom, while the Pen's bathroom is more separated from the bedroom area (with the closet between them), giving more light and sound separation. This matters to me more when traveling with my partner when I might be trying to sleep a bit earlier. Also you have more space for moving around and storage in the actual bathroom in Pen (even though you only get one sink).

In the hallways leading to the rooms, the Langham looks higher end with hardwood floors, etc.:


Vs. Pen:


Inside the bedroom areas, I'd say they are more comparable, with the Peninsula having a slight edge on looking more modern purely based on the finishes, but the Pen still suffers a bit from the constraints of its building: there are (very) low ceilings, not floor to ceiling windows and dated HVAC grates and baseboard heating, etc. The Langham's bedroom decor is very beige and neutral and looks perhaps more dated in ways, but the higher ceilings, cove lighting and more favorable building envelope of the Mies van der Rohe skyscraper allowing true floor to ceiling windows are points in favor.

Langham (sorry for the poor grainy photo and limited angle because it's from 5 years ago):


Pen:



Other thoughts:

• The Langham Club Lounge is quite nice. Not worth $100 / day or whatever unless you're never leaving the hotel during your stay, but sometimes you can get it as an upgrade or rate bundle (e.g. FHR, etc.).
• The ongoing ambulance noise from a nearby hospital at Pen is absurd IMO.
• Pen always focuses on technology and functional layout usability in rooms, especially for business travelers (you always get the printer / scanner / fax in-room...).
• Last times I stayed (2019 & 2022), Langham service showed pretty consistently that whoever was running things really knew how to train the staff to do 5 star luxury hotel service, unlike many US luxury hotels. Pen seems pretty on it too, but I didn't have as much time to compare.