I think that based on all that we know about things, Blingdenstone sounds like the best bet. However, Ezraen does not even know that Menzoberranzan is the drow city, though I do. Based on what Ezraen knows, since the Kua-toa and Duergar are generally considered evil, I think Ezraen would vote for Blingdenstone, and if Shuushar offers to guide us across the Darklake, all the better. However, he also has a soft spot for helping and would be willing to escort little Drum home to Neverlight Grove first.