These are the two hotels I usually stay at in HK. Now, with the Conrad as a Gold I would think the access to the lounge might be doubtful but you should get a couple of nice rooms along with breakfast at the downstairs restaurant which is ok but not great IMO. The Conrad is in central attached to the Pacific Place shopping center which is very nice but my wife prefers to shop at the little shops in Kowloon which is where the Sheraton is. I actually find the Sheraton to be nice rooms and the only thing missing is a proper lounge for Plats. They have a Plat lounge which is just a closed room with a fountain soda machine. I think Plats get continental breakfast at the restaurant downstairs which is quite good. We always paid the difference and got the full breakfast as the difference was not that much and much better breakfast than theh Conrad.
Unless you need to be in the central area I wouls say Sheraton has a much better location as you can walk to many places and with the Conrad you will need to traverse the mall to get to the MTR and then cross over to Kowloon for most of your entertainment options and while not a huge task that train can get full in rush hour. Also, the airport express will be slightly cheaper to the Kowloon stop (if you use that option).
Now, you would get stay/night credit with Hilton for the award stay and would not get that with SPG if that makes a difference.
I do like the Sheraton as it is a decent hotel although I think the main wing is more 4 star than 5 (the towers is more 5 star) and it is in a good location.