Just to update you all on our return; we chose neither the Westin nor the St. Regis in Rome. We ended up for 5 nights (decided to stay whole time in Rome) in the Intercontinental Ville de Roma (directly next door to the Hassler), thanks to Manku's suggestion. Our Six Continents card enabled us to upgrade to 2 adjoining balcony rooms, overlooking the Spanish Steps. Took a quick tour of the St Regis and Westin, and while lovely, they were quite a bit out of the way for us. Was very happy with our selection, as more time was spent on those balconies than anywhere else in the hotel.
As a side note, we had also just come from the Grande Bretagne in Athens. Certainly one of the best hotels I have had the pleasure of visiting. Cannot wait to return!
Robin