The Pen is nice if you want rest and luxury. The Oriental is an institution and gives you a flavor of the old Bangkok of the elite. It's unlike any other hotel in these parts, MO or otherwise. The rooms are comfortable enough and I never had a problem with the service here, but it is old and needs refurbishing in some places. Some rooms too can be oddly shaped although that's probably part of the charm. I love the split-level River view rooms in the old wing, which have a sitting room and huge picture windows onto the pool and the river on one level and the bedroom on the upper level. I have always chosen to stay here over the Pen, as it's just such a special hotel in terms of atmosphere and history; although I would probably choose the Pen if I wanted a truly indulgent weekend.

PS: No, I'm not in my 50s. And I've been staying at the Oriental ever since I was in my 20s.