I think this grammar point needs some rework, I'll list the additions/changes I think it needs:

A)It should be titled under だい, and possibly include んだい separated in the same page, one of the difference being (quote from DoBJG) "Questions with だい, and those with んだい, correspond to questions without のです and those with のです in formal speech, respectively."

B)Another difference is in their construction:

だい can follow only な type adjective stems, nouns and noun equivalents. The following sentences are ungrammatical because だい follows a verb or an い type adjective.

a. *だれが行くだい。Who is going? WRONG
b. *どれがおもしろいだい。Which one is interesting? WRONG

んだい can follow verbs and い type adjectives.

C)DoBJG describes だい as "A sentence final particle which indicates an interrogative word question in informal male speech. " so both the fact it accompanies an interrogative word (誰、どこ、なに etc...) and the fact is male speech, should be mentioned.

D)This is a third, separate usage of だい:

だい can also be used with declarative sentences for emphasis in boys' speech:

a. これは僕のだい。

This is mine.

b. 僕も行くんだい。

I will go, too.