Shield 9mm. You can't beat it for concealed carry. I own several CCW's. The Shield in 9mm is by far the best all around carry gun in my opinion.

I carry other guns from time to time, but if I could only carry one from now on, it would be my Shield.

Go with the 9mm. 147 grain federal HST hollow point will do anything a .40 will do. It's much more pleasant to shoot and ammo is cheaper and usually more available.

With all that said, only YOU can determine which gun is best for you. Hell, I carry a full size Springfield 1911 every now and then. I just love guns. The important thing is that you carry. Always carry!!!!! You can't decide when you will need it.