I just finished converting one of my player's Assassin from DH to OW rules.
In DH, he spent 10,900 xp. After I gave him all the skills, characteristics advances and talents he had in DH, he came out as a 19,150 xp OW character (almost double XP).
I also noticed that in DH, with the "abstract" method, a PC earns 200 xp / session, while in OW it's 400 xp / session.
Do you think it's a good rule of thumb to give a player converting from DH to OW double the XP he earned in DH to "re-make" his character with OW rules?