In short:
RPI can do at most 20000 steps per second, if lucky and with a bit of fiddling (this is from what i read here, i stopped using RPI since version 3B)
Mesa can do 10000000 (10 million) steps per second on any or all pins, if pushed, does 1-4 million for years on end, can use any pin as input or output, does steps, encoder counts, PWM, on any pin (the FPGA part), can be programed as needed, extremely reliable (i have over 80 or 100 or i have no real clue in daily use on industrial machines weighing several tones without a single issue ever for many years), and by far the best support on planet earth in the form of PCW.
Yes i am biased, from experience, no i am not payed by them, and yes any price you see for Mesa boards i have to pay at least twice that, and i pay it gladly for the piece of mind i get with them, i can sleep calmly without worrying something might fail.
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As for RPI, i personally use old "enterprise" PC's and some laptops, so if you can find such things it is another alternative, i can get Lenovo T470 for 120-150 euro, with 14" touchscreen, battery, plenty of RAM and NVME, with built in network jack, for me this is much cheaper than any RPI combo and more powerful and usable.