Both the phones have their pros and cons, I think you should go for Redmi note 4,
Redmi note 4 has the following advantages over Samsung galaxy on 8.
1. Redmi note 4 is available for 10,999 Rs whileSamsung galaxy on 8. is available for12,090 Rs
2.Redmi note 4 has Android, v6.0.1 (Marshmallow), and upgradable to 7.0 (Nougat),whereas Samsung galaxy on 8 has Marshmallow OS
3.Compare to CPU Redmi note 4 has Faster CPU than Samsung galaxy on 8,means more smooth experience on Note 4.
4. It has better inbuilt memory than Samsung Galaxy On8. More memory allows you to store more songs, videos, photos and install more applications.
5.Redmi note 4 has battery which delivers long hours of backup.
6.For security Redmi note 4 also has fingerprint sensor ,this feature lacks in Samsung galaxy on .
It is not like that it is a one sided game, Samsung galaxy on 8 has the following advantages -
1.Samsung galaxy on 8 Has Removable Battery and Redmi note 4 does not come with Removable Battery
Verdict - In my opinion, Redmi note 4, is better overall performance and price ,if you need handset with removal battery than go for Samsung galaxy on 8
You can also compare these devices on 91mobilesXiaomi Redmi Note 4 32GB vs Samsung Galaxy On8
Check the video
I couldn't find any major differences between them. On8 has better display than J7 2016 and J7 2016 has better processor than On8. I'm using J7 2016. Its performance is very good. I have seen On8 also. J7 2016 is slightly faster than On8 and has better graphics too. You can go through this comparison too. Compare. I'm attaching a video which I just found on YouTube. This might help you in picking a best one.