The ASUS ZenFone 2 (ZE551ML) 4GB RAM is the top-spec ZenFone-series model, but the ZenFone Selfie (ZD551KL) has more features that I would consider to be better than the ZenFone 2.
– Selfie front camera beats ZenFone 2 quality hands down. The ZenFone 2, despite also having the Beautification mode, is unable to beautify me enough.
– Selfie front camera can shoot in all other modes available in the rear camera.
– Selfie front camera has LED flash light.
– Selfie rear camera removes noise better, more sharpening applied.
– Selfie rear camera white balance is less aggressive, tend towards warm tones under artificial light.
– Selfie rear camera auto exposure is better.
– Both uses 3000 mAh battery, but the Selfie lasts longer and battery drains slower.
– Selfie battery can be removed.
Selfie’s both SIM slots can support 4G one at a time, while Zenfone 2 can only support 4G on SIM 1 slot.
ZenFone 2 runs on faster processor, so it is more snappy. The Selfie can get rather sluggish, and struggles to perform tasks promptly.
ZenFone 2 supports fast charging. ZenFone Selfie charges with 5V 2A current and will take longer to charge.
ZenFone Selfie does not support NFC, if that matters for you.
Normally, I would vote for the phone with higher-speed processor. In this case, however, my vote goes to ZenFone Selfie because of numerous hardware improvements, especially the front-camera, which makes it a more desirable device for photoshoot lovers. If raw performance is all you want, then it’s the ZenFone 2 that you should get.