The most apparent advantage of an online auction compared to a physical one is the convenience. There is no need to take time out of your busy routine to go and visit the auction in person. Since it is online, you can access and bid at any time.
At online auction sites, there is no wait time to start bidding on a particular car. As soon as the listing goes online, the bidding can start. At physical auctions, cars are shown in a set order, and it can take hours before your desired car shows up for bidding.
Plus, since you are not outdoors, you don’t have to contend with the elements like you might have to at a physical auction, e.g. standing in the summer heat, avoiding rain or hail, or even getting your boots stuck in the mud.