Just go for one plus 3t else u can pick 1+5t @38000 instead of buying the phone 6s@39000(64gb). iPhone 6s comes a9 chipset, now iphones are running on a11 chipset . Moreover iphone 6s is older in my opinion , still it's a good phone but not worthy at that price. If u want a mobile at 39k just go for 1+5t with a dual cam , water resistant, snapdragon 835 (more powerful than apple a9 chipset),18:9 aspect ratio(q4 of this year 2017 smartphone r coming with 18:9 aspect ratio). If u r a camera lover i shall prefer u to buy lg v30 (44k), world first smartphone with f/1.6 aperture( based on my knowledge f/1.6 aperture is a larger aperture which can take photos more clearer in low light).
Thus you know iphone a branded company uses great things for building of its mobiles iPhone 7 uses stereo speakers for better sound quality and oneplus also uses stereo speakers but in case of good sound both are equal