I actually had a 2012, 27" desktop. When it gave up the ghost in 2019, I bought the 21.5" instead. This size is plenty big enough for my purposes. In fact, I found the 27" too large for the "viewing" distance between my body/eyes and the monitor.
Splitting the difference with the 24" might work for me, too, but I have been satisfied completely with the 21.5" since 2019.
