The GH is what one would expect of a good Asian Grand Hyatt - large, business oriented, good F&B etc... but rather unexciting. As I said it is not at the level of GH Tokyo or GH Erawan Bangkok, for example.
The W has the great views, and is a hot spot in the local social scene in addition to being a good hotel. And at suite level, such as the Fantastic Suite I mentioned before, it is definitely “luxury” or at least as close to it as any other hotel in Taipei will get.