Here are the key differences between the three difficulty levels:

Easy
Points to distribute at start: 450
Starting capital: 100,000
Monthly time budget: 80
Starting team guaranteed: 2
High bonus for team hierarchy level
Slight decline in skills (1000)
Faster training success

Medium
Points to distribute at start: 350
Starting capital: 50,000
Monthly time budget: 60
Starting team guaranteed: 1
Moderate bonus for team hierarchy level
Moderate decline in skills (1500)
Moderate training success

Hard
Points to distribute at start: 300
Starting capital: 10,000
Harder goal scoring
Monthly time budget: 40
Starting team guaranteed: 0
Low bonus for team hierarchy level
Significant decline in skills (2000)
Challenging training success