IFI Zen blue vs Bluesound Node 2i

What's the difference between these two devices and will both function as a streamer/dac between android or iphone using Tidal or Spotify and an integrated amp?
From my quick perusal of a What HiFi review, it looks as though the the Zen is just a DAC, and it has to be directly connected by usb to a computer not only to play the files on the computer, or to stream files from the computer program for something like Tidal, but it also gets it’s own power supply from the computer.  I doubt it would be powered by the likes of an iPad, and it would be tethered to the iPad by a cable that has a mini Jack on one end and usb on the other—assuming such a cable exists.
   The Node is both a streamer and a DAC.  It offers Bluetooth.  It can directly attach to a computer by usb but the preferred route is by Ethernet or WiFi to the rest of your network.  You then use the BluOS app on your iPad to control it.  The app rolls in Tidal and every other streaming service manageable 
A few corrections:
  • iFi Zen Blue has only Bluetooth input and is powered by an external 5V power supply. There is no USB or any other physical input, unlike the iFi Zen DAC, which can be powered either by the same USB providing the signal or with a superior low-noise external power supply.
  • Bluesound Node 2i has no USB input from a computer; the USB port is for storage drives only.
  • the iFi Pro iDSD is a true streamer.
In my opinion, the Bluesound Node 2i is the best *value in its class* for a single device streamer-DAC. That said, it's DAC implementation is just meh, and there is no USB output to feed a superior DAD (but there is coax and optical).

The iFi Zen DAC, especially with the $49-$99 low-noise power supply upgrade, is a far superior DAC implementation.