"There is a reason Hikvision are used by a great many people, companies and local authorities - because their products are pretty damned good at what they do."
Hikvision are used because the cameras are very cheap and retailed at many shops and smaller companies specialising in security camera installations had an easy upgrade path from older coax cameras because they could just plug cameras and DVR's into company networks and it was instantly visible with the camera app through internet, due to UPNP and the DVR's transferring all the data through manufacturers own systems for easy access. Maybe with default credentials as well. Scary shit but most small companies don't know better. Or care.
Both Hikvision and Dahua products have been assimilated into botnets due to their vulnerabilities.
The hardware itself isn't anything peculiar - like with any other cameras the IQ is all about the image sensor and optics, and with interchangeable optics it's only the CCD that matters.
I looked at Dahuas about 5 years ago last time, and their only solution to use the DVR's with a web browser was via Internet Explorer and an unsigned Active-X plugin! Also, all communications with the NVR was unencrypted, so you could just sniff the credentials.
If you need to replace legacy (coax) camera systems, the Dahua HDCVI cameras are incredible value for money, and a drop-in replacement for getting FullHD, because CAT cabling would be expensive or even impossible with >100m runs. (ethernet over coax extenders do exist, however)
Dahua NVR's have contained hard coded credentials.
These CCTV products should only be used in closed circuits (=separate VLAN with no internet access and firewalled), and then they're secure(-ish) to use, but the usability will still be poor.
Of course, no matter what the manufacturer is, you should always separate security cameras in their own VLANs.