Verte is my clear favourite and it can get as low as around $150 or low 20K range on points - I think it's normally at a rate that gives much better value than the Bristol in any case, especially on points.

No way I'd stump up $90 or anything close to pick Sheraton over Westin; I would scarcely pay 90 PLN. The location is preferable for easy access to the Old Town and Nowy Swiat, but the Westin location isn't really that bad. I actually prefer the Westin.