Warriors of Chaos lords - do you promote them to demon princes?

When playing as the Warriors of Chaos, do you promote your lords to demon princes or prefer to keep them mortal?

- Lose half your levels and skill points.

- The loss of most of your traits (you keep any for killing legendary lords, but lose the rest).

- Need to regain the Immortal trait, possibly meaning the permanent loss of a lord you’ve spent half a campaign building up.

+ From a roleplay perspective, it feels like they’re fulfilling their destiny.

+ Some powerful skills unavailable to human lords.

Personally, I find Nurgle demon princes to be really powerful, but the other demon princes feel like a step down in power from their mortal versions (even after regaining levels and traits). What are your thoughts and how do you play WoC lords?