Point is, there is no way-- via SPG or any other conduit-- of getting your valuable OnePass miles into AAdvantage at anything even resembling a 1:1 ratio. I personally did transfer hundreds of thousands of SPG points to AA (at a ratio of better than 1-> 1, 1-> 1.25-- as that's what SPG transfers yield) and in the process earned AA lifetime gold and will have AA lifetime Platinum by this year. FWIW, at 2 million lifetime miles (from any source) AA currently also gives you 4 system-wide upgrade certificates-- which is a nice little bonus.

Who knows how long AA will continue their lifetime elite program-- all the more reason to do it soon if one is so inclined. Plus, it's a new elite-earning year-- what a great time to re-evaluate one's carrier of choice.