If you invested that $1900/mo directly for nine years, a 7% return would provide a gain of $288,293 before taxes and inflation. Doing that for another nine years results in a total gain of $825,044 (plus $1900/mo).
If you invested $257k directly for nine years, a 7% return would provide a gain of $224,663 before taxes and inflation. Leaving it alone for another nine years would put you with a total gain of $645,723 and a total balance of $902,723.
I would likely take the monthly amount.