I know that you didn't ask, but my $0.02 is that yes, RasPi's are unreliable. If you use one for as an unattended remote server, it will do you well to include a hardware watchdog that power cycles the device after it hangs. But modern NUCs seem to take MINUTES to boot the BIOS. I had been using various BeagleBones and found them more reliable than RasPi's and faster to boot than the NUCs in the office. But depending…
Regardless, I'd also recommend setting up the hardware watchdog just in case. It's saved me in the past when I overloaded my Pi with a bad cron job.