I've seen the expressions insight into whether and insight as to whether used. Are both correct? If so is there any difference between them?
This is really an idiomatic choice of preposition, so a quick look into Google NGrams shows that "insight into" is by far the more used phrase.
EDIT: After thinking about it a bit more and since just posting an NGram unqualified seems like kind of bad form, there's another question on this very StackExchange that seems to come to the same conclusion, as well as various English sites offering insight into correct preposition use.
Insight into whether is quite common, as is insight on when no comparison is being made. Insight itself implies intuition, and as to implies that you are dealing in absolutes, so I don't think it fits as well.
Related question: To gain insight into or on?