I'm a breath away from not being qualified to post on this thread. All I can do is say that I've been a tube guy and a knob turner, and forever suspicious of digital modeling. Frankly, I'll stand by my suspicions right up to the current generation of modelers, specifically Fractal, that made me change my mind.
When I auditioned the Helix at GC, shortly after it came out, I wasn't impressed and chalked it up to the fact that it sounded and felt like an amp mic'd up in another room that I was monitoring in this room. Granted, I worked through presets only. And, I found some tones that were just fine. But the experience wasn't like I was playing an amp. I was just playing tones, or something. ...Hopefully that makes sense.
It was the Fractal models that were more dimensional and 'live' feeling. And they converted me, reluctantly I might add.
Any piece of gear can be adjusted to sound bad. But I find my AX8 to sound really good, even with the presets - which I often use as the template for my own patches.
Lots of people love the Helix. And the interface cannot be argued with. But I like my AX8.