Some of the default soverigns to pick from are either over or underpowered compared to what is possible to create using the Create Soverign option.

Soveriegn more powerful:

Relias (player will be short by 1 point if creating a clone)

Gilden (player will be short by 5 points if creating a clone)

Sovereigns weaker:

Procipinee (Player will have 5 excess points to spend)

Now I realize that this is beta and things are likey to change, but this should at some point be balanced out. As it is, there would be no reason not to always pick Gilden as your sovereign, since he starts out more powerful than anything you could create on your own.