Let's see, $180 + shipping and at least 2 mags @ about $40 each. That is getting close to $275 -300. Why not spend $100 more and and have one of each? No switchy-changy, no confusion, no forgetting how you are rigged.
I have two Bersa Thunders, a .22 and a .380. They look alike, feel alike, and are almost the same weight, both accurate. I practice with the .22 and carry the .380 with minimum practice. The .22 paid for itself in short order on cost of ammo. There is a lot of carry over from the .22 to the .380. Reason says the same would be true for the "twin" shields. It would take a little longer for the 9mm to pay for itself in reduced ammo cost.