On-premises caterers have a lot of advantages. They work in the same space every day and they’re able to walk directly from their kitchen to the venue floor where your event is being held. This means it’s easy to make last-minute changes or corrections if needed.
But the main thing setting apart on-premise caterers is that they typically offer a lot more than food. Since they are attached to the venue, they have access to its supply of tables, tablecloths, stemware, dishes, and décor which allows them to manage many aspects of the event presentation. They are also likely to provide the bar service if needed.
However, on-premise catering can be expensive. As the official venue caterer, they can charge a premium, potentially far more than you would pay for the same food from someone else.