Have been using Samsung J7 ( Black) for almost a month. The phone is a typical Samsung with crisp screen and good camera both front and back. The screen is 5.5 inches and quite sufficient for reading and watch videos/pictures.Most of the high quality games run smoothly.I havent noticed any lag so far with the games like real racing 3 and asphalt.
It is one of the good phones among the 10-15k price range. But do take a look at the new Lenovo k4 note before taking a decision.