You can not go wrong with either property. I am staying at both later this month as I will be in BKK twice. Both properties have their own advantages.

In particular I love the breakfast buffet at the Grande Sukhumvit. I used to get it for free as a Platinum, but I have heard (unconfirmed) that Platinums get a continental breakfast in the lounge now. I would pay the difference for the full buffet if that is a possible alternative.

The views from the Royal Orchid are picture postcard perfect.

Try them both.