The above post captures it pretty well.
You'll see velocities equivalent to the barrel length to the point the porting starts.
You'll find yourself being asked to move to the far end of the range by the less than happy shooters next to you.
If you thought firing a .357 mag indoors was loud, you'll realize it's nothing compared to a ported .44 Mag.
Ported barrels and firing from a close in retention position are not compatible.
The slower burning powders that give more velocity in a longer barreled magnum pistol are the same powders that given maximum effect in a ported barrel - and those same powders have enough flash that a ported barrel in low light conditions is not a great choice.
I can't speak to ported .44 Mag pistols losing front sights, but I got a great deal on a bubba's Model 94 trapper in .44 Mag that the previous owner had ported. In addition to being obnoxiously loud, it had a habit of blowing it's own front sight off now and then. I re-barreled it shortly after I got, partly to increase it's value and partly because the porting was not worth the almost non existent benefits.
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If you plan to shoot it in tactical matches, porting will increase controllability, but a ported .44 Mag won't do anything in a tactical match that a .357 can't do better.
If you plan to hunt with it, you'll need to use electronic ear muffs on top of your ear plugs so you can still hear sounds in the environment, yet not deafen yourself when you shoot, and again anyone else hunting near you will not take kindly to you.
In general, I think many of the guys who like ported barrels are the same guys who like putting pipes on their trucks to make them several times louder than they need to be. They pretty much annoy the hell out of the rest of us.