The question comes as I start editing the Configuration.h for an updated Marlin and see it defaults to 250000 now. I've been using 115200 up to now and never felt a problem with that. Or is it I just didn't notice the symptoms?
A higher speed at some point brings a higher risk of communication noise, in theory. I could simply test it but thought there should exist some knowledge about this already. A quick search didn't show me evidence, though.
Does it make any practical difference?
The answer is "it depends". In general you want the fastest speed that your printer will support to help avoid possible stuttering during the print. This does bring in the requirement for better/shorter cables.
However, some boards use USB CDC instead of a serial converter chip - for USB CDC the baud rate is ignored and it always goes at maximum speed (12Mbps). USB CDC also includes error correction so it can go at the higher speed. Any board that uses an LPC176x chip like the SKR 1.3/1.4 or Re-ARM will use USB CDC. Some STM32 based boards use it as well, but it's harder to tell which of them use a separate serial chip instead.