Recently released, the M5 is the Banana Pi version of the Raspberry Pi Model 4B, but with a Raspberry Pi Model 3B Port layout and footprint. Like most Banana Pi systems, it runs on their own Raspbian version of the OS as well as a host of others OS, it is recommended to either run Armbian Linux Os or Android.
 
But unlike the Raspberry Pi 4, the Banana Pi comes with some features that the R-Pi does not:
CPU                  Amlogic S905X3 Quad-Core Cortex-A55 Processor, up to 2.0+GHz
GPU                  Mali-G31 GPU
Memory            4GB LPDDR4
Storage            16GB eMMC flash onboard
                 MicroSD slot with support for up to 256GB expansion  
Network            10/100/1000 Mbit/s Ethernet
                 Optional WiFi USB dongle
Video Output      HDMI 2.0 (up to 4K@60Hz with HDR, CEC, EDID)
Audio Output      3.5mm jack and HDMI
USB ports            4 x USB ports
GPIO 40 pins like the R-Pi
                 GPIO (x28)
                 Power (+5V, +3.3V and GND)
                 UART, I2C, SPI or PWM
 
The only issue I see is that the Wifi is only possible with a separate USB Dongle, otherwise it would be equal to the R-Pi in many respects.with 4GB of RAM, it puts it within the realm of the R-Pi 400 computer system and the 4G R-Pi 4-4GB. It makes up the lack of the Wifi with Gigabit Ethernet.
 
Unfortunately Banana Pi sells it for around $67 (Plus $5 Shipping from AliExpress). For a few dollars more, one can get the 8GB R-Pi4, twice the RAM for just few dollars more.
 
From what I seen however, it excels in video processing used in media streaming and emulation. And in gameplay under Android, it is hard to beat. Those complaining about game buffering, one should keep in mind that it is an under $100 system playing games meant to be played on multi-thousand dollar systems. One has to seriously think about where one's priorities are at if they do not see the comparision of the two.
 
For me the problem is its price. It is a bit steep for me. But it maybe worth it in the end for those who can afford it.
 
Banand Pi Webpage on the M5: http://www.banana-pi.org/m5.html
M5 at the AliExpress Store for $67: https://www.aliexpress.com/item/1005001871842695.html
A review of the M5 by ETAPrime: https://www.youtube.com/watch?v=bCrRhziPSc8