My girlfriend and I will be staying in Singapore for a night next month on our way back to the US. Looking at Singapore Airline's website, there are Singapore Stopovers available in different categories of hotel. We'd most likely go for the second-highest category at $47/person. It includes this choice of hotels:

Hilton, Inter Continental, Marina Mandarin, Meritus Mandarin, Pan Pacific, Regent Swiss�tel The Stamford, and The Oriental.

Location is our #1 priority, and a close 2nd is comfort and service. My guess is that either the Pan Pacific or the Oriental will be our best bet. Any thoughts?

 

My personal choice for the best hotel in SIN is The Raffles Hotel...however from the list you have I can recommend the Swissotel The Stamford (formely the Westin). It is located opposite Suntec City and within walking distance to Orchard Road (shopping) and Clarke Quay (restaurants). There is also a MRT stop just outside. Ask for a room on the upper floors for some great views. you should at some point during your stay have a drink in the bar on the top floor at sunset...stunning views of the city.
The rooms are reasonably big and clean (but what isn't clean in SIN) and well equipped. The breakfast buffet (included with SIA stopover package) offers a decent choice, although during my stay there last year it was a very busy and rushed.