I agree with the other reports on here - the Westin is THE place to stay in Sydney. We're also in your age group, and are normally 'W' stayers, but in this case the location and quality of rooms at the Westin is far better. Head over to the W for a drink or two in the bar, but sleep at the Westin.

The bar at the Westin is disappointing -- staid and never very busy -- but there are several great bars within a 5-minute walk of the hotel.

Make sure you book yourself into a heritage room (or ask upon check-in, if you're eligible for an upgrade).

I've produced photo reports for the W and Westin in Sydney, if you're interested in knowing 'what you'll get'. Here they are:

Westin Sydney Photo Report

W Sydney (Wooloomooloo) Photo Report