In reality, most people can't afford hiring one of those detectives. A cheap one will cost you about $200 per hour. If you wanted him to follow your spouse for days, the way you see it in movies, you'll be bankrupt in no time. When people hire a detective, they have to be very careful about the hours and days they hire him. These days and hours must have the highest chance of success to be worth the cash. And unlike movies, real detectives don't have an easy time finding what they are looking for.
But, does
mobile spy work better than a private detective? Yes, it does, mainly because it's not a human. It doesn't need to rest, sleep, eat, or go to the bathroom. It doesn't have the need to stretch the investigation in the way a private detective would be tempted to (since, you know, he's being paid by the hour). And finally, it gets you all the details you need and stores them in a website so you can read them whenever it's convenient for you.