From what I've heard, the biggest drawback is that if you have more than a handful of cameras that you want to record in reasonably high definition, then none of Ubiquiti's hardware can keep up.
The other pretty big problems are no backup solution, video exports limited to 10 minute clips, cloud account and Internet mandatory (at least for initial setup). What drives me bonkers is no support for valid SSL certificates because they don't want you to have to worry about that or something. It breaks the protect app when you don't use their snakeoil default.
I'd still be using Unifi Video, but they broke the iOS app for like a whole year so it was use protect or switch over to something that took in RTSP from the cams.
Their new Unifi Protect Network Video Recorder [2] is supposed to do 50.
[1] https://store.ui.com/collections/unifi-protect/products/unif...
[2] https://store.ui.com/collections/unifi-protect/products/unif...