The feature the 4 has which the Neo doesn't which matters most to me is 'touch to confirm key operation' when used via USB. I'm quite surprised how little this seems to be known - a hardware key which will sign anything a potential piece of malware or malicious actor asks for without question (assuming said malware is able to steal the PIN or get access to the appropriate agent socket which is not too much of a stretch) is a lesser improvement over pure software keys (sure, you can get the same effect by plugging and unplugging but thats a pain).

On the other hand, NFC is pretty much essential to me for use on an android phone. If this has both then I will look carefully at upgrading.