As far as I'm aware, the difficulty rating for the SNK Neo-Geo soccer games is
Sidekicks2 > Sidekicks3 > Sidekicks1 > Neo Cup '98 -- not sure about U11 since I've never put time into it.
So, after doing a 1cc of Cup98 for fun with Hong Kong, I've decided to tackle Super Sidekicks 2 and win...