The difference between using SODE from the GSX menu and SODE from its own menu, it's that when GSX calls SODE, it will send to SODE its own GSX airplane customization, while when using them from SODE, it will use the SODE internal database of airplane models.
Usually, the GSX customization is more precise, since it's customized for each airplane and you can easily edit it but, if that SODE 3rd party jetway has been modeled using the SODE own database, you might see some difference, but you cannot be sure of *another* SODE jetway, maybe made by another scenery, might not instead work better with the GSX configuration, since not all jetways from all scenery developers are made in the same way.
AI will always use the SODE configuration, since GSX doesn't store or handle custom configuration for AI airplanes, so they always work using the generic SODE database.