I've been trying to remember who said this, but I can't, so apologies to you:
"When you're stuck in a fire, would you rather have a fire extinguisher, or a picture of one?"
I think a Gold ETF is a great way of trading gold, but nothing else. If you've been buying physical gold (and can easily get hold of it when needed - ie, not in a bank vault) then you probably already understand the benefits. So don't swap one for the other.
Like you, I buy physical, but at times I use ETFs to go short or even double short if I'm feeling extra crazy...
As far as HSBC is concerned, I don't have anything against their product, but I personally trade US ETFs, just because of the much, much larger volume (hence liquidity) available.