Honestly, if I saw a difference I'd use HDMI. I mean, why wouldn't I if I have the facility, right ? Fact is, VGA looked the same to me so I just stuck with it.
I tested with a 30GB m2ts rip I made of my Hobbit : Desolation of Smaug bluray. Went straight to the scene with the giant spiders and then to the scene with the barrels in the river. Lots of action and fast moving images, and both HDMI and VGA performed brilliantly. I'm not arguing that HDMI should be better, I'm just saying that from my own personal experience they were both equally good.