I would check those rates against something like Asia Travel or Expedia first - on the few occasions i've looked, the SQ rates haven't been that special, especially for the higher end hotels.

Trasport around Singapore is generally very easy - cabs are cheap and plentiful for the most part, whilst the underground system is good too. As such, your precise location isn't a massive issue.

Closer to a MRT station is better as you have more options that way. Of the hotels on the SQ page, I would probably be tempted by the location of the Furama as it's by the river and if I'm thinking of the right hotel has a whole bunch of bars nearby. You could even walk to Orchard Rd, although would be a bit hot...

Note also that if you do go down the SQ package route, it includes a seat in coach to the hotel, but a cab from the airport is only S$20 so you may prefer that option.