In my experience, the cables and dongles were prone to loose connections. You had to fiddle with the plugs to make sure they had a proper connection.
Selecting the right resolution was also problematic. Sometimes the native resolution of the projector didn't work for some reason, leading to blurry images.
I remember one time there was a weird issue where only half the image was shown. Another time, the image showed up with wrong colors (not sure how that happened).
HDMI isn't all rosy either, poor cables also cause connection issues. I had one cable that only worked in one direction. That was very odd. But in my experience HDMI connections are way more reliable than VGA connections.
(Maybe projectors and laptops also became more reliable, can't say for sure)
HDMI is a pain in different ways, and these are just examples in my house. Keeping track of version 1-2.2b has become a small chore. Perhaps it is time I burn it all down to claim insurance and start over.
As soon as you go past 1080p@60Hz, as you pointed out, you can't just grab any cable. I suffered a great deal from this moving to 4K screens. Sparkles, drops, and black screens are usually a connection problem. Some smarter device/driver combos will work around a bad connection by dropping colour information to fit into the available bandwidth, some won't.
I have one 4K display where HDMI 1 is, well, HDMI version 1. HDMI 2 (as in the second port) is HDMI version 2 and will actually display 4K@60Hz.
I have TVs that need fiddling to get the proper native resolution and framerate. Some need game or PC mode to disable overscan and show the whole image.
Currently on my desktop connected to a 4K TV, if I try to set a game to 1920x1080, the driver seems to pick something strange and I get no image at all. I'm not sure who to blame here.
I still have devices that won't do 4K@60Hz, they're limited to 30Hz. It's a device limitation, fine. A Raspberry Pi 4 will output 4K@60Hz but not by default. You have to enable it in the firmware config.
I've resorted to putting tags on all my HDMI/Display Port cables with the version/anything special cause I was sick of trying to figure out if the problem was the device or the cable being old.
VGA can show wrong colors when one of the pins isn't completely connected, which can happen if you're used to needing to use force to get it connected and you just jam it on and bend a pin. Some pins control specific color domains, one time I bent and pin and blue completely disappeared from my monitor. Thought it was a gamma gun going bad until I noticed the pin.
Check with the AV supplier for the venue and you will find that most conference projectors are intentionally lower native resolution than entertainment projectors. They are different types of hardware for different markets.
I like to prepare the presentation using a laptop or monitor having the exact same native resolution as the projector will have from the beginning.
Selecting the right resolution was also problematic. Sometimes the native resolution of the projector didn't work for some reason, leading to blurry images.
I remember one time there was a weird issue where only half the image was shown. Another time, the image showed up with wrong colors (not sure how that happened).
HDMI isn't all rosy either, poor cables also cause connection issues. I had one cable that only worked in one direction. That was very odd. But in my experience HDMI connections are way more reliable than VGA connections.
(Maybe projectors and laptops also became more reliable, can't say for sure)