To answer this thoroughly, first, a Bartender must be defined and then differentiate a standard bartender from an Event Bartender. A standard bartender works at an established location that is open to the public. The Bartender’s general responsibility is to prepare an already existing bar setup and create and serve drinks that the establishment has predetermined to be available. Part of this is creating a welcoming atmosphere that encourages patrons to enjoy themselves.
An Event Bartender specifically goes to the location of the event or party and has to set up the bar from scratch. This means unloading supplies, cutting fruit, and preparing any ingredients into ready-to-access formats for fast and efficient bartending. Most often there isn’t even a bar station at the location so a portable bar would have to be rented. Then all the supplies would have to be brought or delivered. An established bar is usually already half prepped at least, and designed with optimal equipment settings to quickly service the bar as quickly as possible. As an Event Bartender, you have to optimize your setup yourself and every Party is a different setup. Therefore, any setup optimization is based on the experience and creativity of the Event Bartender and the equipment available. It takes more time to set up an Event Bar than a standard Bar by far, and breaking down an Event Bar is also more work than an already established Bar Setting.

At an event, you have guests, not patrons simply because they come specifically to that occasion which is normally a private space with an RSVP. Another distinction is that Bartending at an Event has a personalized Menu and Gratuity Policy based on the host’s preference. A tip Jar at a Wedding Reception will not be filled like the Tip Jar at a Tavern if at all. Some client prefers to have a Tip Jar to create a more “Bar Ambiance” feel to the event, while others prefer to include gratuity in the service so that their guests don’t feel obligated to pay anything at the Event. Also, the number of guests an Event Bartender can handle is much higher than a regular bartender because it’s usually an Open Bar setting so there is no need to keep tabs or process payments for the guests. An Event Bartender worth their salt should be able to handle about 75 Guests at an Optimized Open Bar Setting (assuming regular mixed drinks).
Always consider reputation (and by extension experience) when hiring an Event Bartending Service. These factors mentioned severely will affect how well your event bar turns out. You can always find a cheaper alternative from 3rd Party sources but you’ll see what you paid for when there’s a long line building at the bar, and by then it is too late to replace the bartender with someone that knows what they’re doing. Always make sure you’re hiring quality professionals when planning an event.