For me, they both meh, but the icon does have a larger screen, so will be better. The font face changing on Wiim seemed better. Wiim in general seems to have a more feature rich and intuitive app/software. Both show volume UI similar. Wish it was larger though. But I am 10 feet away, and the only things I care about are volume meter and clock. Rest is pretty much unreadable and useless if like me you are primarily using it via HDMI arc.
Since WiimU doesn't have airplay, I will have to use my apple tv to stream and can airplay to the apple tv also. I can Google cast directly to WiimU. Since Node doesn't have Google cast, I was using my Google TV to cast. I could airplay directly to node. So in that regards I loose out on 1 and gain the other lol. I am an android phone user and an iPad user. In an ideal world each of the devices will have Google cast and airplay, maybe they will some day via firmware upgrade. Till then I am stuck with using either the Apple TV or Google TV.
The icon's top controls are quite unintuitive, borderline poor design/accessibility. WiimU round button control is better.
Forgot to mention, 1 big thing missing from WiimU is lack of USB input. If that's important, Node icon will be better. Since my wiimU is connected to a DAC, I will just use the dacs USB input if I need to connect directly to the speakers. But yeah, its definitely an additional device and more wires. Node was just a single box, albeit 3x the cost.