Sheraton used to have a very bad reputation and was feeling dated, it is now being refurbished so it will likely be improved on many of the reviews here. You still have the situation that the JW is a better/nicer hotel (and higher brand standard), and you will look onto either the harbour view of Kowloon (with a few buildings in the way) or the peak (green and pleasant), plus the MTR is accessible directly via the Pacific Place mall. Sheraton you should get a nice view of Hong Kong itself proper, but its a few steps outside to get into the MTR.

Hence I agree with moondog , choose based over what experience of Hong Kong you prefer between the two parts of the city. Personally as a first time tourist I'd choose to be on Hong Kong island and get the famous city view on a star ferry that will take you to very close to the Sheraton hotel . If I'd been many times before to Hong Kong Island or liked shopping I would choose TST to explore a more local experience, temple street market etc.