We stayed at 4P. Westin was opened for business the day we checked in 4P. It is separated with 4P by an entry way to the underground garage. So location-wise, the 2 are identical.

With 4P at 1/2 of the point cost it is enough saving for us to choose 4P over W. The breakfast at 4p has almost all the things pictured above although not as elaborately displayed. They dont have good cereal selection if this is your thing. They have a cook constantly making sunny side up with careful attention to various doneness (far better than what Sheraton on the Park in Sydney did). The cook also can make your egg dish request as well as other requests that are relatively easy. I asked to have some wilted spinach and the cook happily did that for me.

W is too quirky to us even not considering the 100% higher point cost. W is very close to the North Quay station for the free City Hopper (the terminal station on one end). 4P/Westin is very close to the Eagle Street Pier station.
Location wise, 4P/Westin is closer to the city center where the shops and local eateries are (the Queen Street Mall - pedestrian area).