Current trend is light and handy, so 20" is very popular. I like 24" on sporters and 27" on long range guns. Muzzle blast from the only 20" was in a 6 BR and it was horrendous to say the least, shock wave concussion.
This is a personal thing, no right or wrong, what ever floats your boat.
When I’ve had 243’s rebarreled the barrels are longer, not shorter than the previous one.
A 24” barrel is the minimum, and a 24” barrel on a 22 Hornet is joy to shoot.
