I would recommend the Conrad, to stay within the Hilton Brand, since cabs and the MRT are so cheap anyway, since your chances of an upgrade as a Gold are guaranteed almost. At the Hilton, I had an issue, but then kindly received an e-mail explaining the situation from the front office manager and offering to reassure me on any future visits.

The Hilton is good by Singapore standards and perfectly located for shopping, and you will get breakfast coupons if the executive floor/lounge is full (and it always seems to be).