A nice Symmetricom or ptf unit is going to offer much better time accuracy and holdover accuracy than those cheap units from China. The really cheap ones have no OCXO so time will drift fast during GPS outage. You get even better holdover accuracy with Rubidium but that's really only worth it if you need a real ref clock for test equipment. Expect to pay at least $500 for a cheap unit with an OCXO.
Obviously most people need no holdover accuracy so a cheap unit is fine. Most people aren't running data centers in places where GPS jamming is expected. Although it's not uncommon for truckers to be running GPS jammers that can inadvertently knock out a whole sea port.
I have a very lovely Symmetricom in my rack that has a busted GPS receiver but still provides NTP and IRIG-B using a Rubidium source as it's 10MHz reference.
Obviously most people need no holdover accuracy so a cheap unit is fine. Most people aren't running data centers in places where GPS jamming is expected. Although it's not uncommon for truckers to be running GPS jammers that can inadvertently knock out a whole sea port.
I have a very lovely Symmetricom in my rack that has a busted GPS receiver but still provides NTP and IRIG-B using a Rubidium source as it's 10MHz reference.