GPS collars have some drawbacks as far as finding runaway, lost or stolen pets. They are primarily made for hunters to keep track of their dogs while working which means the hunter is in close proximity to the dog and constantly monitoring. And I assume a hunting dog has some extensive training unlike the pets which tend to stray.
Battery life is poor (a few days) on most of them. That means you would have to check/change the battery almost daily just to be certain it won't die when you need it most.
You must be near a phone or computer to get an alert. So if you're somewhere with your cell phone off, or you don't check your email often, you're out of luck. And if you're far away when you get the call, you probably won't get home in time. If your unit doesn't come with a handheld receiver, then someone has to stay near the phone or computer if a cell phone isn't available (or it's battery is dead).
Some are bulky and can get hung up on brush or fences making them a danger to the dog.
The collar must be on the dog. If removed or if it comes off it won't help you. You may as well assume a thief is going to remove the collar and ditch it.
Most GPS collars have a specific range of only a few miles (depending on terrain) so may not be helpful if your dog running fast, or roaming around in hilly country, or is stolen.
Dogs rarely stand still and it takes a while (depending on the model) to update the screen display on the handheld receiver. So what you see is not very accurate. And by the time you get to that location, the dog will be somewhere else. If the dog enters a building (like when some kind soul takes your dog in), the GPS won't work.
It's not abnormal for GPS to be "off" by several meters in some locations, so you don't always get a precise location making a moving target hard to spot especially in the dark.
They give a false sense of security.
Be sure to ask a lot of questions before throwing away your money.
Frankly, I think you're better off supervising the dog whenever it's outside.
My son works for Garmin and gets to test their products. Neither of us was impressed with their collar for pet use. Great for hunters though.