At higher level there is no huge difference between 2 teams...
A 4 star team will be say 140 in overall quality and a 5 star team will be 145...So that is very small difference...
But at lower levels there is a huge amount difference...Say a 4 star team with rating 20 and a 5 star with 25...That's a huge difference...
So you can buy weaker player and that will affect your team quality hugely...
And at higher level there are only active managers...So the competition is very tough...