All three smartphones are excellent devices, offering good performance, excellent cameras, and premium designs. So the difference is in its price, and that really matters at the end of the day. For $539, OnePlus 5 comes with the latest Snapdragon 835 processor, a full metal bodied design, dual rear cameras, and 8GB RAM. Thats half the cost of iPhone 7 Plus.
Under 15k budget u will have Lenovo p2 that meets your requirement.zuk z2 dosent have 5.5 inch display otherwise it is a Powerful device having a Snapdragon 820 processor.honor 6x does have a duel camera set it is good if you want to buy a camera specilized phone or vivo but vivo isn't good enough to be a lag free smart phone.and Moto g4 was released in early 2016 it's backdated I don't recommend to buy.if you wanna go for Redmi note 4 it does have a good processor and better battery life out of any other phones you listed but it doesn't have very good camera though pics taken from it are pretty good and this phone lacks good ram management.
do not install un necessary apps or low usage apps...and reset phone on every 6 to 12 months... it will increase your battery as well as reduce heating issue.
no..mobile with pixel density of 367ppi , chipset of snapdragron 653, and no optical stabilisation is not upto the mark...with these features c9 pro is worth of around 20000...with 27000 one can go with one plus 3T
