Hikvision and Dahua seem to be the lines offering the best range of quality and features - both offer 4K cameras if you want to invest in a 4K display & graphics card - in fact if you're willing to drop $42,000 both offer thermal imaging security cameras.
i had played with cameras years ago (D-link) and they were not stable and hit or miss affairs, having to setting them (configuring) back up too often.
Just recently, to get my feet wet, i went with a NEST camera (owned by google and the same people that came out with the NEST thermostat). The NEST advertises 1920 x 1080 resolution - unfortunately i could never get more than 1280 x 720 with it. Then found out from a friend the Nest, as it's wireless, is the easiest wifi device to hack into (he's in security). Then i learned the voice 2 way comm feature is effectively worthless on the NEST. Because of google's ever growing thirst for info, the stream from the Nest goes first to their server and then to your PC, which means there's a 2 second delay in the voice comm. BTW - None of the camera makers offer full duplex comm - your cellphone is full duplex, so you and your bud can both talk at the same time. With the camera voice comm, to greet a visitor to the front door, you have a "mike" icon that you clik, then talk. Then you have to unclik it on the NEST (on the Hikvision you hold the mike icon with left down cursor button, when thru talking, simply release)...but back to the Nest - as the signal first goes to nest's server, then to the camera's speaker, there's a 2-3 second delay. And the visitor, if he answers too quickly, while you'll see their lips moving, you won't get the first few seconds of what they say. I actually made a small formica sign to put by the camera telling visitors to wait 5 seconds before responding.
Now comes the real contention with NEST - if you want to keep all the features like motion alerts on your smartphone, you have to subscribe to their cloud storage svc ($10/monthly or $100/yearly) - if you don't, you lose those and voice comm at the end of the 30 day "free trial" cloud subscription. Oh, almost forgot, Nest does not allow you to record the video footage to your own server, nvr or computer.
The only "pro" with the Nest, it was real easy to set up - but motion sensitivity adjustment is limited, and their software isn't that stable, and their servers aren't always responsive - sometimes i waited 5 minutes for a response from their server to see who had come to the door.
THere are aftermarket software vendors offering management software (Blue Iris is one) that offer better control, in terms of motion alert zones, sensitivity etc, than the camera's software. But Nest does it's best to make it not work with BLue Iris by constantly recoding their software to kill the "work arounds" that Blue Iris and other programs find to record the nest video stream. Go over to youtube and search for "Nest & Blue Iris" - there are a number of posts in comments section alluding to the fact that nest has a team of engineers dedicated to killing "work arounds" as they pop up.
after researching both Dahua and Hikvision i went with Hikvision - main reason, a) Dahua's USA website is a joke - searches never pull up what you later find there on your own - it kind of brought back memories of 1990s english manuals that came with chinese products.. 2nd reason, i downloaded their configuration tool software to see how well it worked - scanned it before opening, virus ware said it was safe. Within 2 seconds of opening it, Emsisoft virus ware went crazy with alarms. I spent about 1.5 hours using the malware removal utilities over on majorgeeks.com to clean out the spyware - and there were two "DHCP" files that were "call home" .exe files.
The hikvision camera i went with has 2588 x 1560 resolution, 2 way audio comm, - prices for an outside dome or mini-dome run about $165 thru $400 depending on features - i wanted IP camera with PoE capability (ie can power it over the ethernet cable, it has it's own built in PoE splitter circuit, and with a switch with PoE ports, it simplifies my wiring to each camera. And for the record, i've scanned for trojans, spyware etc (using the majorgeeks utilities) and found none with Hikvision's software.
Hikvision tech support was real good - fast answer or access, and pretty knowledgeable - i got some help on the first camera and after that first one, it was fairly easy. You could spend 8 hours going thru the adjustments on their config software - it's that intense.
I've now installed 4 hikvision cameras, and got one more to go - i've been real happy with hikvision.
but one warning - you'll find Hikvision and Dahua cameras, sold on amazon but direct from hong kong and china vendors for 60% of the USA distributed units - Hikvision USA will not service any tech support requests nor service the warranty if you have a defective camera, you're at the mercy of the asian vendor.
and be careful of IPTALK.com - they convinced me they're shilling for dahua.
last warning - ignore "night vision" capability claims, ie "IR vision good to 100 feet" etc, or at least cut their claims in half. And if you're going to use the motion alert feature with a camera, forget the night vision capability altogether - the IR leds attract moths and spiders climbing all over the lense, setting off the motion detection alert. For the cameras that i do employ the motion alert feature, i have 5000K Led light bulbs lighting the area - for whatever reason, the 5000K (Kelvin) doesn't seem to attract insects.
fwiw