We will have a comparison of the specifications of Arduino Uno and the STM32 Blue Pill Board.
Arduino Uno and Raspberry Pi are in different leagues altogether. Arduino is a microcontroller, while R-Pi is a Single Board Computer. R-Pi comes with its own operating system. Arduino has no OS, it can simply run programs compiled for the Arduino platform (which means C and C++ programs in general). There is no point comparing the two, but still let’s see the difference in specs, to drive the point home.
Arduino Uno has 2 kB of SRAM. The first model of R-Pi had 512 MB of RAM.
Arduino runs on a 16 MHz clock, while the recent versions of R-Pi run on about 1.5GHz of clock speed.
Arduino runs on an 8-bit microcontroller, while R-Pi runs on a 64-bit microprocessor
Arduino needs external shields for WiFi and Bluetooth connectivity. R-Pi has these onboard.
Arduino can be powered via your laptop. R-Pi needs a separate USB Adapter (since it consumes upto 1.25A at 5V, depending on the variant.
R-Pi can have multi-cores (the variant in the image shown above has 4 cores), and even GPU support.
R-Pi has HDMI ports (for connecting it to a monitor), Audio jack, micro-SD Card slot, Ethernet port, and a lot more.
I think the above points would have given you a clear picture of how vastly different Arduino Uno and R-Pi are.