So there is not really any difference in the two. I would like the newer footswitches as that alone is a BIG FIX from previous models but not enough to get me to shell out another $500. There is no better value than a L6 HD500 on the market, and anyone who owns one will tell you that, but there should be an upgrade or trade-in plan for those who just bought the previous version if there is not that much difference in the two.
I will say if you don't own one or the other or are new to L6 the tone flexability of having some of the best effects, mods, amp packs etc, your missing out. I fought going digital for years always carying around a huge wooden pedal board with 2-3K of effects on it, with sounds dialed in and having a pain in the lollipop to setup "Stereo Effects". When the HD500 came out I would go jam with people carying sometimes 2 different AMP Heads, and this huge pedal board and spend 30-45min minimum setting it up, and friends would come in with an HD and be playing in 2min sounding damn near as good, and be able to expand well beyond my capabilites as they had 20+ different AMP and cabinet combo's.
The real power of these things is PC integration and edit's of stack's and setlist, which is really awesome and where I think L6 has helped revolutionize guitar sounds. They also make it possible to share sounds with other L6 users at customtone.com, which I just actually learned about, lol!
They really make all the work and effort I used to put in to finding a "perfect sound" seem archaic, when I should have been practicing on technique or learning new styles to bring to the music I create.
Sound is such a funny animal, and what you can produce on one PA, may sound nothing like another PA etc, so it's funny we all spend so much time on it.
** Sorry for the rant, I guess I didnt want to attack L6 for not relasing more in their update without also giving them the props they deserve as a company. In reality these things are a bargin at double the price.
One question I must ask though is, if I get a 500X, just want to be sure a 500+ or 600Z doesn't come out this XMAS without an upgrade plan, lol