I've stayed in the tower and the older wings. The former is definitely 'nicer' in the sense that it is more recent. That being said, the wings have a certain charm that I prefer.

Overall, the place is an institution. You really cannot go wrong. The Peninsula has a timeless, classic charm to it that I have not found in other high-end business hotels.

One splurge that I enjoyed: get the Peninsula to pick you up in their Rolls Royce. It is expensive, but it was quite the experience.