How do you decide between oral vs nasal route of entry for bronchoscopy with BAL with moderate sedation?  

Either approach is acceptable. The nasal approach has the advantage of placing the scope right above the larynx more easily but the oral approach has less risk of bleeding in patients with coagulopathies. 

I trained in the early 90s. Where I trained the nasal route of entry was preferred. My experience is that patients cough less, require less sedation, and the scope is easier to guide and direct from the "stable" base of a nasal insertion. With proper nasal preparation complications related to nasal ...

If it is a simple look bronch or BAL, we use the nasal route with moderate sedation provided there is no coagulopathy or thrombocytopenia.  In most other cases, we prefer the oral route. Make sure an assistant is doing a forward chin lift, so the tongue is pulled anteriorly and the vocal cords...

The question asks about "bronchoscopy with BAL." If bronchoalveolar lavage is the only procedure planned, then the nasal approach is faster and, I find, requires less sedation than an oral approach.