Firstly I'm not that technical guys cannot comment much so my lay man's view...
On paper the specs are good but not sure of actual usage. IMO it could outperform 4g version but there are few question in my mind...
How will it handle MIUI?
Does any app on Android uses entire 8 core? Is it really required or for that matter 2gb ram to run device smoothly for day to day apps & small games?
Why can't the OS be optimized for 512mb or even 1gb ram & basic dual cores for day today usage in order to run the device lag free for months together. Heard Kitkat is smooth but can experience few lags on my Nexus 7 2012 too.
For me 4 core snapdragon will suffice even 2 krait cores will do

just the OS should be optimized well to run lag free.
Had Lumia 520 for 1 year & totally happy with it except battery life. Could play Asphalt 8 without any lags but I cannot dare to install it on my Redmi 1s.