Be Excellent To Each Other

I got a monitor recently. It had the old style d-sub connector. Do these offer somehow inferior picture to dvi or hdmi or is it just people changing the connection style on things for no good reason?

Yeah, d-sub is VGA, so it's an analogue signal, not digital

Looks just fine to me anyway. I wonder if I would notice a difference with DVI or HDMI...

Depends on the resolution and what you are doing.

I usually use DVI for my computers, but the Revo retro box is on standard VGA as the Eggbox is using the HDMI on that monitor and the Revo has no standard DVI only VGA and HDMI. Can't say it makes much difference for what I'm using it for. Picture is pin sharp, images are solid and colours bright.

However the PC in my office looked worse when I took it to VGA from DVI (the Mac needed the DVI). Softer picture and black text on grey suffered. Colours also suffered slightly as well.

So "suck it and see" is my suggestion. It depends on the video card and the monitor.

On my 1920x1080 monitor, I can see a difference between VGA and DVI/HDMI, but HDMI and DVI are indistinguishable to me.

Isn't that because they're the same signal, just different connectors?

Yes, it's exactly that, although on some of the more TV-like monitors they might have different processing on the two pathways. Yes, that's retarded.

Analog VGA is also more susceptible to interference than digital signals. At high resolutions (1600x1200) with cheap-ish cables in the past, I've had to route the cable away from power leads to avoid a 60Hz flicker on the screen.

Same video signal - HDMI also carries audio. But then you already knew that.