Which one should I buy, a OnePlus 2 or a Samsung Galaxy J7 Prime?

Lets compare both Phones

OnePlus 2:
It has 5.5 full HD display, Qualcomm MSM8994 Snapdragon 810 Octa-core (4×1.56 GHz Cortex-A53 & 4×1.82 GHz Cortex-A57) (CPU) , Adreno 430 (GPU), 13 MP / 5 MP camera, available in 2 versions {(16 GB/3 GB RAM) , (64GB/ 4GB RAM)} ,Non-removable Li-Po 3300 mAh battery and fingerprint sensor.

Samsung galaxy J7 Prime:
It has 5.5 full HD TFT display, Exynos 7870 Octacore 1.6 GHz, Mali-T830MP2 (GPU), 13 MP / 8 MP camera, available in 2 versions {(16 GB/3 GB RAM) , (32 GB/ 3 GB RAM)} ,Non-removable Li-Po 3300 mAh battery and fingerprint sensor.

Verdict:
You should go for Oneplus 2 Because snapdragon 810’s performance is much better than the exynos chipset. i am fan of Samsung’s SUPER AMOLED display, But don’t know why they have’t given super amoled display in this phone. If you are samsung fan then i will recommend you to buy Samsung galaxy j7 (2016).

You can read reviews of both phone here:
OnePlus 2 review – A phone with few equals || Samsung Galaxy J7 Prime Review

Buy From here:
Oneplus 2 || Samsung Galaxy J7 prime