Master League in PES 2010 has taken a step back IMO.
You can no longer create your own league, nor have promotion and relegation: its one league choice out of 4.
In PES 2009 each league divided itself into two divisions, so less games per season. Now, one league, one division and 18 to 20 teams, which makes one season far too long.
Maybe in PES 2011.