I also just completed a 3-night stay here. I found the rooms to be quite small compared to the Renaissance. Bathroom/rain shower is nicer though.

Marriott Sukhumvit will have a 40th floor Exec Lounge and a 45th-floor skybar arguably "cooler" than what the Ren has to offer but they won't be open for another several weeks.

Breakfast buffet spread is not up-to-par with what is offered at the Ren either.

Nice hotel, but unless you have a specific reason to stay in Thong Lor I'd still stick with the Renaissance.