The HI location is better than the W Marriott location in my opinion. The Chit Lom subway station is right in front of the hotel. There is upscale shopping close by (on the riht hand side are some of te nicer shopping malls), normal shopping with a good choice of tailors etc in the small shopping center opposite (walk thru the train station to cross the road, Starbucks in there), restaurants (some fairly good independent places in the basement of the IC hotel next door).
Usually i stay in the IC (which sometimes has really good rates), but also have been in the HI and JW Marriott. I would prefer the HI over the JW (but got the JW several times really cheap on priceline).