If you are looking for a gun you can use for IPSC, here are some things to consider for fit, assuming you are holding the gun aligned correctly (axis of bore in line with axis of wrist):
Place the gun in hand with the beaver tail pushed down into the web of the
hand. See where your finger falls on the trigger. Ideally it should be close to a 90 degree angle between the surface of the trigger and the surface if the trigger finger(last digit of the finger). This means perpendicular to the axis of the gun, so you can most easily pull straight back a long that axis without disturbing the sight alignment.
Also, check to see if the finger will rub against the frame above the trigger guard when you are firing. If there is any contact there at all, look for another gun. You will never be able to fire an accurate shot at speed if you are rubbing against the frame.
The modern IPSC grip technique is for the most part, a high thumb set-up to maximize the leverage advantage, and this means that both thumbs are pointed at the target, one atop the other. If the gun has a frame safety the shooting thumb will ride on it. If not, it will ride on the weak hand thumb. Place your thumb there and note if there are any sharp edges on the safety or the beaver tail or anywhere in the loop between your trigger finger and thumb. Sharp edges or pressure points will cut or bruise in recoil.
With the thumb still on the safety or in the correct grip position, note how the grip feels in the hand. If there are any air spaces between the surface of the shooting hand palm and the grip surface, the gun will try and twist in that direction in recoil. Ideally, you want a maximum skin-contact fit...a skin/gun weld if you will, so look for a gun the offers this.
If there are any spots on the grip or beaver tail where you feel pressure points, these will likely become uncomfortable in recoil, so look for a gun the fits the hand in the same way a good shoe fits the foot; no pressure points to rub you raw or bruise. Note that in IPSC you will likely have to grip tape the gun so that you can reduce slippage, and this adds a small amount of thickness. You don't want to start out with a gun that feels like you are trying to curl your fingers around a fence post to start with; it will just get worse once you enhance the grip surface (Yes, I know that not everyone tapes their grips. But if you want to be competitive, check and see how many people will shoot a polymer framed gun in July without grip tape. It's like trying to hold on to an eel).
Once you have a short list of guns you think you like, ask around and see who owns one and if they will let you try them out for a few rounds. Trying a gun for fit in a gun store and actually firing it are two different things. I've held guns in my hand that felt great but were horrible to shoot, so try before you buy to avoid having to sell your investment at a loss.
Good luck with your choice. I hope this helps.
R