I've had both the Thompson and the M14 (which I converted to an M1)for a few years and they are both excellent guns. The choice is in what you would rather do. Be part of the base of fire team or part of the flanking team. Base of fire team go with the M14... flanking team go with the Thompson.
On another note... Since you will be painting the M14 stock when you convert it to the M1 it really doesn't matter if the M14 stock is OD, black, or wood.