The Arduino Uno R4 Minima seemingly has a purpose of eventually replacing the Arduino Uno R3. It’s a 5 volt board with the same form factor as the earlier Uno that seemingly offers more performance (speed and memory capacity) at a 25% lower price point. People are finding flaws in that it has lower current driving capability and sluggish peripheral performance. The Arduino library “talks” through a Renesas firmware abstraction layer rather than accessing the hardware directly. So along comes the Arduino Uno R4 WIFI, shown at the left, below:
At an additional cost which puts it slightly more than the Nano 33 IoT on the right, this new Uno R4 variant has an ESP32 Wifi/Bluetooth radio and a cute 2D LED display. I show the much smaller Nano 33 IoT here because it also has a radio. In my admittedly limited testing the Nano performance as a web server is much faster.
Now in any application beyond a breadboard, the LED display of the Uno R4 isn’t going to be viewable. You want it as a separate board peripheral. I expect the radio slowness is caused by the inefficient interface in the Renesas microcontroller. The only thing the Uno R4 has going for it is 5 volt operation, but here is a secret — the ESP32 is a 3.3 volt part so level converters are necessary. Not so with the Nano on the right.
Unless Arduino or someone (won’t be me in this case) streamlines that sluggish, bulky software library, I’d steer clear of either of these boards. Buy the original Uno, or one of many Chinese clones, for an introduction to microcontrollers (classroom use?). Otherwise buy one of the more modern Nano size boards like the Nano Every (5 volts, very inexpensive) or Nano 33 IoT (ARM core, 3.3v, WiFi/Bluetooth).