There is really only one downside to web-based auction software - you need an Internet connection at your venue. Most of the time (here in 2014), that’s not an issue. But occasionally, you may do a 4th of July event in the middle of a field, or hold an event on a boat on a lake.
In those cases, a mobile hotspot can come to your rescue. Here’s a recent article from Lifehacker, listing their current favorites: