1) Grasp empty gun with firing hand, pointed towards floor. Pick out a spot on the wall, close your eyes, and point the gun at it. Now open your eyes. If the sights are aligned with the spot, that's good.
2) With eyes open and sights on target, tighten your grip on the gun. If it does not squirm around to the side, or up or down, that's good.
I'll bet one of these three guns fits better than the others; that's the one you want.
On a secondary note, a frequent novice mistake is to forget how annoying it is to carry a heavy, bulky gun for any length of time, especially if it has to be concealed and kept tight against the body. There is a lot to be said for a slender, light weapon if you are going to be carrying it a lot.