IFI Zen blue vs Bluesound Node 2i

IFi makes no streamers that I know of.
That would be the difference.

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.

iFi currently sells the Zen Stream. It is a streamer only and does not have a DAC.