Thanks for the review and pics. A couple of comments.
The upgrade from Deluxe to Grand Deluxe at St. Regis gives you a view of the Sports Club. I find the view quite nice, so would consider that a meaningful upgrade.
No mention of the pool - did you check that out? It's spectacular. The nicest of any property I've stayed at in Bangkok and big plus for this property if you're looking for an urban vacation.
The issue I've had at SGS my last two stays is the crowds of tourists from the mainland. Breakfast at Orchid Cafe resembled a rugby scrum and the pool was completely overwhelmed (and the staff visibly unhappy about it). I stayed one night at St. Regis last visit due to lack of availability at SGS, and found it to be a serene escape from all that.