Brand new here! Just went through the decision between purchasing the HD500x and Helix LT myself. I've read a lot about each unit (using the full Helix for most of that info)
Although the Helix LT looks fantastic, and has a great UI...I think for now the POD HD500x will suit me just fine.
I actually did something a bit different to get reference for just how good the HD is. I went back to when the original POD HD500 was released and watched those videos from Paul Hindmarsh and others and read reviews from the same time. I was sold immediately.
It's easy to get sucked into the hyperbole a new system like the Helix brings and think that it is VASTLY superior to the one before it (POD HD). The sounds don't say that. It is no doubt better, but anyone in my position should really go back in time to see how much people raved about the HD and also watch Robert Renman dialing up a Hendrix tone on a cheap Squier strat. I watched that video right after watching a Line 6 rep do a Hendrix tone on the Helix. Renmans was better on the HD500 IMO.
Anyway, just saying hello from a happy soon to be 500x owner. (delivery next Monday!)