Thanks JimH,
It's more than a connector, it's also a protocol, same as SPDIF is a protocol for transmitting digital signal.
Now I know some people will say it's digital signal so bits are bits, there's no difference between SPDIF & HDMI!
Don't fall for the digital is perfect mantra (this was the marketing message first used to sell CDs). The difference between them is got to do with the timing clock which is embedded in these digital signals, this is the reference that is used to decode the signal from digital to analog sound.
Now if this is different from the clock speed that the music was recorded at or fluctuates during playback (called jitter) then the sound we hear will be corrupted. Tests have shown that small amounts of & the type of this jitter are noticeable by the ear at a far lower levels than was first thought.
Jitter causes a haziness to the sound & probably also a fatigue after listening for a while.
I believe there is a difference between the jitter level on SPDIF & HDMI, hopefully for the better, but I don't know yet!
Just after the best sound possible! I'll move onto video later (there is such a thing as video jitter also)