@ OP and others, I have been reading through the thread and must say, that yes, VGA is still widely used, but that doesn't mean that there hasn't been much progress over the years. It all depends on the hardware, the GUP and monitor, and the application you are using. If you not using a mid to high range video card and playing video games or watch full HD action movies and things like that then you yes, you wont be able to tell the difference. Then comes the HDMI standard itself, there are older HDMI 1, 1.1 and things like, and then you have the cable quality... So there are many factors that can give you possibly worse experience than VGA.
As far as audio is concerned, the gpu you are connecting to has to be capable of providing audio over HDMI, not all are. If it is then you will see a separate sound source and you will have to tell you PC to use that as the primary sound card. Then you monitor, even if it has inbuilt speakers, it wont necessarily accept the HDMI input as its digital and has to be processed at the receiving end , as compared to analog over aux input.
If you have a 4k monitor and a 4k capable video card, if you want 4k at 60hz, then you will need a HDMI or Displayport, those are the only connector/standards that have enough bandwidth to support 4k @ 60hz