https://img474.imageshack.us/my.php?image=nomad7fp.jpg

Here is the chart. And here is the link on the chart:

https://forums.totalwar.org/vb/showthread.php?t=74103

The nomadic and pastoral system differs mostly in recruitment. One allows you to recruit infantry and elite cavalry while the other allows the recruitment of "raider" type nomadic cavalry.

Pastoralism also allows more city improvements while nomadism restricts this.
Both types of government will affect your family members traits and happiness depending on their preferred lifestyles.