Do you have AS? If so SQ credits very nicely into an AS account.

Unless you have plans for lots of DL travel next year, getting the extra bump to Silver isn't worth routing via AZ.

Also what are your dates? I'm seeing the DL direct priced at a very reasonable $2.2k with what looks like a 3 or 4 day stay. Admittedly the DL 767 on that flight is not in the same league as SQ but that would give you DL if that matters and would give you a direct flight.

I still would advocate SQ and credit to AS