Honestly, Bell will go forward with the Invictus in any case. They are not going to shut down 50 years of attack helicopters history just for that.
Invictus is lean and can propably be sustained with a couple hundreds of orders. That should be reasonably doable in the next 20 years by themselves (think Airbus receeding market).
On the other side, Sikorsky offers something new with a bonus in performance. If they don't get an order, their design will die and it would probably means that a design opportunity has been lost.
IMOHO, there is nothing to choose. It's only logical. (what it should be, by the way)