The STM32F3 is the mainline family of STM32 MCU’s. Not as cheap as the STM32F1 but pretty close. And for the added buck you get a Cortex-M4 cores with DSP and FPU extension. If you don’t speak technical abbreviations, an FPU is a Floating Point Unit. If you’ve going to use “floats” and “doubles” in your code, you really want an FPU as it will seriously increase performance.
In practical terms, getting started with the STM32F3 is easy : there’s an Arduino Nano sized Nucleo-F303K8 module, a regular Arduino sized Nucleo-F303RE, and a large Nucleo-F303ZE, and that’s just for the cheap options.
I use those Nucleo modules very often, so I’m going to write down a few of the things I’ve learned along the way. Don’t be fooled : those modules may cost less than ten Euros but they are based on very complex microcontrollers.