My parents and I spent 4 nights in BKK in February. We split our 4 nights at the Peninsula and the Oriental.

Breakfast-
If your breakfast is not included in the room rate at the Oriental, I recommend that you hop across the river and enjoy the excellent buffet breakfast at the Peninsula.

Not that the buffet breakfast buffet at the Oriental is bad. Far from it. The food is fine. The setting is riverfront, which is a very nice way to enjoy breakfast. Service is fine but lacks the warm Thai hospitality the rest of the hotel is famous for.

The breakfast at the Peninsula is wonderful. The food is much more impressive. Case in point, the pastries are first rate and fresh, where as at the Oriental, because it's an outdoor buffet in a humid environment the pastries become pale and wilted. Also, the outdoor cooking stations at the Peninsula do a very good job of keeping the warm buffet dishes fresh and appealing. You can sit on the riverfront if you want. Service is very attentive.

Lunch and Dinner-
I'd avoid the dinner show at Sala Rim Naam at the Oriental. The food isn't really that good and I've heard that there are better shows in BKK.

The lunch buffet at Sala Rim Naam however is excellent. The food was exquisite and the service was very gracious and a bit on the formal side. I think the buffet cost something like THB600 or THB700. Expensive for BKK but worth it.

I love Thiptara at the Peninsula. I love the wood pavilions. I love the warm, unpretentious, caring service. I love the evening riverfront setting. I love how they try so hard to accommodate to guests' tastes.

The Celadon at the Sukhothai was good but I didn't like it as much as pavilions. The service was a bit sterile but the food was very good. I didn't find the setting to be decidedly Thai; could have been Maui.

We had dinner at Shintaro at the Four Seasons. It was fine. Not overly impressed.

Afternoon Tea-

The afternoon tea at the Peninsula was a bit disappointing. The pastries and sandwiches weren't that good. And this is the first afternoon tea I've been to where they charge extra for refills of sandwiches and pastries (my afternoon tea experiences have included the Peninsula HKG, ORD, Harrods Georgian Room, etc.).

I really like the Authors' Lounge at the Oriental. Having tea there is really a trip to another era. The pastries that come with the tea set are good, but the a la carte French pastries were divine.