There's not much limitation at all with a 4 inch. As for Glocks which I use in IDPA, I find the balance and the quicker draw of the G19 actually helps vs. G17 or G34. The sight radius and lower recoil help in the larger guns. It's a trade off. Why will you shoot IDPA? To win your State Championship or to get better with your defensive handgun. If it's the latter, shoot the G19 and don't worry about winning.

I've seen people win with a G19 though.

IMHO A slightly heavier longer gun is typicaly easier for a beginner of moderate size to handle and shoot well. They yield slightly better accuracy and velocity where as the small gun hides easier.The only advantage a small gun offers IMHO is it might be a little bit easier to conceal. Many people conceal full size 5" barrel pistols with relative ease. I personaly carry a 4.5" only because M&P45's are not available in 5".Unless you intend to get a CCW Permit I reccomend a full size pistol. Just be sure it fits your hand properly.

i like the natural point-ability (is that even a word?!) of a 5" barrel. i have glock 17L and absolutely love it. however, if you are going to compete you may want to check the rules to see what the regulations are for your gun...

I would go with the 5” gun for the following reasons:

• Longer sight radius, which translates to better accuracy.
• The size of the gun will help you in managing the recoil of the gun.
• The 5” barrel will give you better flexibility and selection of ammunition that you can shoot in matches.

With a five inch 9mm you can shoot production in USPSA and be extremely competitive or you can shoot IDPA in Stock Service Pistol and be competitive as well. I am a Grand Master IPSC shooter and have been shooting competition for a while, my recommendation is to go with the 5” gun if you intend on shooting matches with it. If you are getting the gun for concealment than that’s a different story. Good luck to you and I hope to see you at a match sometime.