Syncing orders between the two apps would keep your sales inventory up to date with each other. However, unlike with product syncing, you are only able to do a one-way sync with orders. On the order syncing setting tab,   you have the option to choose a sync between: Vend to WooCommerce, WooCommerce to Vend  or disable the feature. See Syncing Options for WooCommerce and Vend for more information.