I know this isn't one of the original two being compared...but I recently checked out all 4 properties (SOTP, Marriott, Westin, and Pier One [Autograph Collection]) in Sydney and Pier One wins hands down.

SOTP felt dated to me; the lounge was busy and I hated having to have an attendant do every drink versus just grabbing it yourself. Also, the lounge manager mentioned they have at least 50 Platinums stay there every night during a work week and even some weekends - so take that as you will for VIP treatment and upgrades. Really cool that the lounge has outdoor balconies, though

The Westin has a much smaller and more private lounge that seems to be used less. There is an attendant but you can take your own stuff. They also have COKE PRODUCTS! Service was impeccable but very few suites available

The Marriott had great service too, but their lounge is on the 2nd floor - limiting view - compared to much higher lounges at SOTP and The Westin, which offer better views. Upgrades also seemed tougher at the Marriott, for some reason. I also didn't care for the immediate vicinity of the Marriott given all the construction and such, but it's maybe 2 blocks walking from Circular Quay

Pier One was my hands down favorite. Sure, it lacks a lounge - but they offer an amazing choice of food welcome amenities - it is such a boutique property with excellent service - and the views and location right under the Harbour Bridge in the rocks area cannot be beat. They also don't seem to have many folks with status as I received amazing upgrades, including to their Presidential suite. Can't say enough good things about this property - skip the other cookie cutter brands you know from everywhere else and stay here. The breakfast has coolers full of fancy juices, every variety of organic milk you can find, barista coffee service, etc. Really good.