I still don't trust Hotwire's 4* to be the same level as Priceline's 4*. Thus, I would use Priceline and bid. And you'll likely still undercut that $97 for 4* from Hotwire anyway. Would not recommend 3* anything in SF; 3* in most large cities are far too variable for my taste.
We bid for "Boutique" level on Priceline for our stay a few weeks ago and got a room at Villa Florence for $75/night (plus the tax/fees). We thought this hotel (run by Kimpton) was just fine for that price and the location just off Union Square on Powell St. seemed ideal.
I don't think the level of service/amenity here was really less than most 4* places, although there are things I don't typically use like gyms, etc. which may play into other people's choices. For downtown SF, 4* is typically seen as the better value as bids for Boutique are often in a similar price range. We settled on it partly because we liked the idea of these type of places but also because I thought it narrowed the possible locations somewhat plus gave us more opportunities to rebid (vs 4*).
See
http://www.betterbidding.com/ for some extra help and recent bids.