At 7 yds it isn't so noticeable to me. At 50 feet, I seem to have much better groupings, and it is noticeable. Both barrels are quite accurate, and the main reason I bought the barrel is for it's tighter chamber, and different rifling. I can now load lead without any apprehensions. I shot my buddies 17, and the34 does have less recoil, and again, appears more accurate. Many competition shooters choose the 34 for good reason.
I have a couple of questions for you related to your gun.
First, what sort of groupings were you getting with the stock barrel?
Second, if you've shot other 9mm Glocks (particularly the 19), what's the recoil like on the 34? From a physics standpoint, it should be less but I was hoping you might be able to shed some further light on that.