I would like U22 and U20 ... if that means until 22nd and 20th birthday.
That quite coincides with some "breaking years" from what I've observed.
If you make a third one, I would prefer under 24 or even 25 ... I mean there are many players improving in these ages,
and as the list is not about top-top players but rather looking at an extensive list of players, I would personally like it best.
To know which players approach the top-100 especially. The players who approach the very top everyone knows them anyway
Maybe that's even the list I would personally
prefer, even though I understand that some may be shocked by that kind of youngsters' list.
I don't think it's useful to go in younger ages than 19 in current period.