'Suzy' and 'Susie' have the same pronunciation, so you just need to decide which one looks better.
'Sue', 'Susie' and 'Suzy' are all short forms of 'Susan' or 'Susannah'.
English names are chosen entirely by how good they sound. English names don't have meanings (with a few exceptions, most of which are girls names which are the same as the names of flowers), so your name should just be what sounds good to you.
Apparently my parents named me Joshua entirely because they thought it was the least likely boys name to be misspelled. My sisters were named for the same reason.
If your Chinese name is 'Su', then 'Sue' is probably the best option. Only go for something more complicated if you think it sounds better. If you do choose a more complicated name, then you do have the option to use the long form formally and just 'Sue' informally.