Some people say the peripherals in the F411 are nicer than the F103. The big deal is 128K of ram instead of 20K (not to mention 512K of flash instead of 128K). The processor runs at 100 Mhz instead of 72.
In November of 2020 I ordered ten based on the STM32F411 and am patiently waiting for the package from China. These were "cuiisw" boards with a micro-USB and 19 pins on a side. A very nice thing about these was that they had mounting holes in the corners.
These no longer seem to be available. What I find now are boards by WeAct. These are different with USB-C and 20 pins on a side. They have no mounting holes (which does make them slimmer). In November of 2023 I ordered ten of the WeAct boards. They arrived 11-13-2023 and look very nice.
Both my Cuiisw and the Weact use the same chip, the STM32F411CEU6.
There are also black pill boards that simply have an STM32F103 on a black PCB, these are really blue pills and are an annoyance.
Worth noting. The STM32F411 is superior to the F103 is almost every way. The "almost" is that the F103 has dual ADC units and the F411 has only one.
And the F411 has floating point! The Cortex-M4 gives you the ARMv7E-M ISA, instead of the ARMv7-M of the M3. Both the F401 and F411 have a single-precison FP unit! What does this mean? Not much probably, to me anyway. The main thing is that the M4 has DSP oriented instructions (the M3 had some but not all), namely "full saturation arithmetic" instructions, and SIMD DSP instructions.
Tom's Computer Info / tom@mmto.org