I have owned several ported ("C" model) Glocks, and still own a G17C. The porting does not really reduce the recoil (the sensation of the gun coming back into your hand), as much as it reduces the upward flip of the muzzle. If a person is already fairly good at firing rapidly and accurately, a ported or compensated weapon will allow them to shoot followup shots even faster in some situations; in other cases (such as multiple targets, where it takes longer to swing to the next target than it takes to recover for the next shot) it will not really help much at all.
As for the flash and muzzle blast, cheap practice/target ammo will flash quite spectacularly in a ported weapon, but quality defensive ammo has flash retardants added to the gunpowder and is not "flashy" at all, even in ported barrels. And once you get above a certain point, loud is loud; if you are target shooting with decent ear protection, neither ported or plain barrel shots will bother you. If you pop-off any ammo WITHOUT ear protection, well, that un-ported barrel will get those bells a-ringin' just fine, too.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)