Ok but again in not nerd terms sir
There are two microcontrollers that are commonly used for our custom keyboards, the 32u4 (used for QMK,TMK and O2D) and the 32a (used for BootmapperClient/ps2avrGB and Jigon).
From my personal observations I came to the conclusion that the time from when you press the key to when it registers on the computer on 32a implementations is a bit longer than on 32u4 implementations.
In the grand scheme of things this does not matter for 99% of users, but if you are playing rhythm games with very tight timing windows and are used to the faster one it makes a very big difference.
Let's say your timing window is 30ms, which means there are 15ms before and after the perfect timing that it still counts, let's just assume the increased delay is 5ms higher (this is NOT the actual value as I can't accurately measure it). This effectively makes your hitwindow 5ms smaller as well as making every hitsound appear 5ms later than you'd expect it, which will make everything feel wrong.
Q: "I don't play these games, why would I care?"
A: If you don't use any of the other features QMK offers that BMC or Jigon do not offer you have no reason to, even for normal competetive gaming it does not make any significant difference.