J series performance is quite good, no hanging or freezing issues, but minor occasional stutters in UI occur, but nothing major. Price is very reasonable considering that its Samsung.
Currently only non warranty model has LTE, and both sim slots are 4G supported, i use Warid and Zong 4G without having to switch sims physically. I think Noir Z10 has only one 4G enabled sim slot AFAIK.
The best thing about Galaxy J5 is its design, the display replacement is done from front side and does not require you to open the phone screws, motherboard or anything at all. So even after display replacement, the phone remains completely sealed and untouched internally.
In most other phones, display changing requires removal of lots of other components from motherboard or even the whole motherboard sometimes, which literally ruins the phone. I think J7 has the same display repairing way too, i will confirm tomorrow.