Many amateurs come across QRZ when they start or when they get into working HF to help with logging. QRZ has a great logging system that many people consider to be their LOG of contacts. QRZ’s logging system is really meant to help make confirmations similar to LOTW or the original online QSL site eQSL.cc.
Not that long ago QRZ redid the logging system and it became a very complete logging system that does indeed have value. However, if you have learned anything about computers you know you need backups. Logging onto QRZ only gives you access to that data as long as QRZ is online and still in business. Is it going anywhere? I doubt it but you never know what can happen.
Using a logging system on a PC or other device that pushes to QRZ, LOTW an eQSL may be the better choice. It is not complex to configure and once setup usually works seamlessly giving you a local backup. (Still back it up once in a while – I use dropbox but many other solutions exist)
Some people go as far as to consider QRZ an authority on amateur radio licenses. It might come to surprise you that it can be used to make fraudulent accounts and has been. Many people have used QRZ to create fake personalities and then sell equipment, collect the check and never deliver.
Never assume QRZ is a call sign authority because it is not that.
In the US the only authority on call signs is the FCC database. When dealing with selling or buying gear and you need verify a call sign, I suggest you rely on the FCC database. I have no remedy for out of the US dealings.
Another thing to consider about QRZ is that it is not complete or perfect. When dealing with 1×1 call signs a person can request a page for a 1×1 call sign and they will be granted it if they properly obtained the rights to use a 1×1 call sign. Having the right to use a 1×1 callsign is not done by QRZ it is done by the different groups that have been given authority under the FCC such as the ARRL.
The online database and authority for this is here:
http://www.1x1callsigns.org/index.php/search
QRZ also does NOT include call signs for all users in the world. I am not an expert on how it feeds call signs into its system but I know many DX contacts are not listed in the QRZ system.
In summary don’t quality a station based on QRZ stats for something critical like operating a call sign for field day, commerce with other hams or checking that LID on the repeater who is swearing like a parrot. Instead learn to use the FCC database for the tool it was created to be, an official copy of your authority to operate.
https://wireless2.fcc.gov/UlsApp/UlsSearch/searchLicense.jsp