In summary
Vote blue no matter who:
Pro - Democrats more likely to win. Things won't immediately get worse.
Con - Democrats have no incentive to do anything other than what their wealthy donors want.
Result - Things don't get worse now, but eventual rightward drift is guaranteed because the democrats will do nothing good and the republicans will win eventually.
Vote blue only if X:
Pro - Democrats have an incentive to do something other than what their wealthy donors what, in theory.
Con - Democrats less likely to win.
Result - Democrats might do something good if they win. Rightward lurch is possible if they lose.
Can we please stop litigating this now?
Edit: The "best" approach would ultimately depend on the relative effectiveness of influencing democrat policy via primaries or whatever, and I don't think the answer is immediately obvious. I am not advocating one approach over the other, I just want people to stop pretending the answer is obvious.
I think you mean:
velociraptor = dpositionraptor/dtimeraptor