The Shield is a great gun, period! The small mag is perfect for concealed carry and the 8rd is nice at the range. Why do you feel you would need to "move up" to .40? I've owned .40's and don't care for them at all. There more money to feed and I don't like the snappyness of them (I do like .45 though, different feel). There is NOTHING wrong with 9mm in a good defensive round. Don't play into the whole bigger is better crap. I wouldn't advise carrying anything smaller than .380 but aside from that your good. You'll hear people go on and on about speed and ballistics and blah blah blah, because they somehow forget that human beings are soft and you won't be shooting at a brick wall or an armored surface in a self defense situation. Buy a good hollow point and practice! My daily carry is between my Shield 9mm and my Bodyguard .380 (when at work) and I don't feel under gunned at all.