A) Ortiz's ages 36 through 37 or 38 seasons at market cost plus Lars Anderson's trade value
B) Lars Anderson's ages 24 through 25 or 26 seasons at barely above MLB mimimum, plus quite possibly two draft picks
Plus in A you have to find a replacement for Papi when he retires, while in B you just keep Lars through his prime years.
Hopefully Papi can go someplace and play a few more years a la Vlad in Texas, because right now it's hard to imagine plan A as the better choice. The timing for Lars to succeed him couldn't be better.
There is no guarantee that Beltre resigns, therefore revisiting the notion of Youk to 3B, Lars 1B, and Papi @ DH. I'd have to think that goes a bit against the pitching and defense approach of this year but certainly is a viable option if Lars continues to perform.