Black Eagles because most of there cast seem interesting alongside the main lord of the house Edelgard in terms of face value.

Now the reason why I am not choosing Golden Deer or Blue Lion is...well...I list them out.

Blue Lions: Dimitri seems so clitch I am not going to lie but his timeskip can be interesting if done right but...I am worried that they will screw it up. The cast is....good but sorry Black Eagles are better. 

Golden Deer: Love Claude but the cast don't seem that interesting to me on face value (besides a few). 

So yea go Black Eagles!