4 cores or 8 cores?

[TkSilver]

The redmi note 3 has the more modern GPU and CPU 64bit and should be vulkan compatible (driver and android veraion dependent)

The OnePlus One is using a top teir processor just 2 year old one though instead of a new mid teir one. The 801 is a faster processor with an older gpu and no 64bit or vulkan support.

The m3 note is using a processor that is not even a comparison so unless you can get it for 1/4 the cost of either of the other ones and want to seriously compromise I would not consider it.

Which is better? The OPO is the powerhouse of the past and handles PPSSPP well for most android compatible titles and is a solid choice. The redmi note 3 might end up the superior choice if vulkan support and some other enhancements give significant performance boosts.

So it is up to you on whether or not you want more performance today or the possibility of better performance in the future