Doorbird D1101V was 671.00 Euro (flushed mounted, salt resistant front) and it has the worst image quality and mobile app speed over LTE.
It has big backlighted bell button and IR which can works all night. It overheats.
It send one mobile notification to IOS devices. Notification don't contain any picture.
It uses server located in Germany (no P2P/open ports config). It works as standalone device (no indoor station requirement).
Open documented API, working web hooks, big number of integrations (Web, ONVIF, RTSP, MJPEG, most popular home automation system have integration with Doorbird)...
Configuration only via mobile app.
HIK DS-KD8003 was about 210 euro with flush mounted frame. Second worst image. Good speed in mobile app over LTE.
It has big backlighted bell button and IR which can work all night. No overheat problems.
It send one mobile notification to IOS devices. Notification don't contain any picture.
It uses P2P or open ports. It DON'T WORK as standalone device - it require HIK indoor station - which works as voice server, push notification server and proxy to HIK Connect (P2P).
HIK offers many models of indoor station (for 120-250 euro extra) - and the more expensive have nice look, good screen technology (IPS) and modern User Interface.
This model is not ONVIF compliant (only HIK private protocol + RTSP), there is no web config page (closed port 80), no open documented API.
Some options can be setup over IVMS (more on PC, less on Mac), the rest is configured in indoor station.
Dahua DHI-VTO2202F-P was about 300 euro with flush mounted frame. The best image. Good speed in mobile app over LTE.
It has metal round bell button which is NOT backlighted. IR turns on only for 30 second after someone push bell button at night. No overheats problems.
It send one mobile notification to IOS devices. Notification don't contain any picture.
It uses P2P or open ports. It WORKs as standalone device (no indoor station requirement).
Dahua offers many models of indoor station (180-220 euro extra), but all are very cheap looking, old screen technology (TFT) and very ancient User Interface.
ONVIF compilant, SIP server&client, works with external SIP servers, RTSP, MJPEG... I found documentation for Dahua web API - but web hook implementation is more complicated.
Configuration via web config page. Mac SmartPSS see this intercom but don't offer any device config/live view...