Global Queue and File Exists

I understand that the Tools | Settings | Transfer | Files | On File Exists setting does not apply to the global queue, so if you are downloading or uploading it will not prompt you if a file exists even if you have it set to ask. My question: what does smartftp do if the file exists and you are using the global queue? I have noticed that it seems to skip if the file is already there and is the same. However, if the file is there but different, it seems to overwrite. Is it looking at file size and/or date/time?