I'm also a fan of the St Regis in Chengdu, the breakfast is very good, convenient location and very good treatment in general for platinums. I also like the bar area, excellent selection of alcohol (though pricey). Having said that, if the JW is significantly cheaper you could always go there and have a slightly worse experience but only marginally worst location / slightly older (I stayed there a few years ago, pre-merger), you probably won't go too far wrong with either of the hotels.