First, there are exceptions to every rule.
The equivalent in women is probably 17 versus 20, or perhaps 18 versus 21, but that’s just an illustration and not an exact comparison.
Regardless, for most people, there is a tremendous amount of maturity that a young man gains between those 2 ages you mentioned, in the three years from 20 years old to 23 years old.
So, first and foremost, the difference is much emotional maturity.
However, that 3 years of additional learning and life experience should not be discounted either. That’s 3 years in a yeshiva or multiple yeshivos (multiple rabbeim, varying hashkafos, different inter-personal experiences, et al.) as well as, for some, college. And 3 summers working as a counselor or in an internship of some sort. Or perhaps not all of that.
But you don’t have any of that by the age of 20 (in most cases). But you could have it (including a college degree and the attendant work and discipline that requires) by the time you reach 23.