It is a good question, I had the same when I first heard about it.

I think lots of people keep both installed:

• the default one is good for managing server related things
• this one is good for daily use, especially for any other users you might have

What I liked:

• feels much faster and smoother
• UI is nice and clean
• download manager works nicely, as another user mentioned. You don’t need to open a separate app to play the files