Though the two aren’t terribly different from one another, the way unshielded twisted pair cabling and shielded twisted pair cabling cancel out electromagnetic interference is. Just like any other type of cabling, the two not only have their pros and cons, they have conditions where one is better applied than the other.
Shielded twisted pair cabling, or STP, has a metallic foil that encases the twisted wire pairs inside a cable. This protects against electromagnetic interference and allows for a faster transmission of data. Unshielded twisted pair comes without any type of shielding at all but is still very capable of handling imbalances that interfere with data transmission.
Since STP cabling works by attracting electromagnetic interference and neutralizing it with a grounded cable, problems can arise if and when that cable is improperly grounded. This will more or less toss its ability to cancel noise right out the window. This type of cabling is also bigger and more sensitive to work with than UTP cable. To make the best use of shielded twisted pair wiring, a knowledgeable cabling installer will likely put it to use in industrial settings where the surrounding equipment gives off elevated amounts of electromagnetic interference.
As mentioned, unshielded twisted pair cabling has no foil shield and relies on the way the pairs inside the cabling is twisted to cancel electromagnetic interference. Since UTP cabling would be more susceptible to electromagnetic interference in industrial settings, it is considered the better choice for office LANS and similar network cabling systems. They are also smaller than STP cables, easier to install and a lot more cost-effective. And, they can transmit data just as fast as shielded twisted pair cabling.
When properly installed and maintained by a reliable data cabling contractor, both unshielded twisted pair and shielded twisted pair will do quite well in their applications.