Lets look at the situation objectively:
If we do not make playoffs we get ~10th pick.
Making playoffs leaves us with 15-16th pick, and higher trade value for our current players. If you are trying to trade a player on a bad team with gaudy stats some say he has good stats only because of a bad team. However, this argument no longer applies if one makes playoffs. Thus value of our current assets increase by making playoffs. There is also a clear benefit in developing coach and young players. Finally, by making playoffs Boston becomes more attractive to free agents.
Basically, the choice boils down to this: 5 slots pick improvement vs better valuation of your assets, experience, better free agent destination
I prefer playoffs, but I can see how one would want to go for the picks. It is a matter of choice.