That it is online. that is it. It is still less convenient than most offline methods though due to the problems outlined below.
Every event (even during the same procurement process) requires you to register a new user
Most of the secure pages come from unsigned domains A MASSIVE security risk
The entire process is cryptic, it is unclear what is required by the customer and what is just ariba trying to get you to buy into their platform
There are 5-10 different places you can login with different landing pages. There tends to be only one you want
It is incumbent on suppliers to understand the ariba naming conventions for their own software
commonly used browser plugins break it
it doesn't work in all browsers
Internally we refer to the Arriba system as the "stone tablet and chisel system" because that's how advanced it feels.
Unless you have massively specific requirements, don't. Your suppliers will think less of you or worse yet simply avoid the hassle of working with it all together.
zero benefits in fact my company has chosen to exit procurement processes that use this system where the value to us is not extremely high.