Yes, both are incredibly capable units and when tweaked and setup properly will be more than sufficient for any application. I will disagree that there are no inherent sonic/tonal differences between the two. Call it fanboy speak, snobbery or delusion. I've heard it which is why I chose the AX8 over the Helix.
Storytime:
I was a longtime user and advocate of Line 6 products going back to the POD 2.0 and floorboard. I really didn't want to have anything to do with Fractal, in my opinion they were overpriced, overhyped and a lot of the users were self-absorbed, egomaniacs. I needed a multi-effects unit and after a couple of years trying to make the Line 6 M9 work, I decided to try the FX8 and it blew me, and the M9, away.
When the AX8 was introduced, I thought 'meh, still overhyped' and was extremely happy when the Helix was released. As I did research, read reviews, listened to audio clips and videos of different amps and comparisons, I noticed the AX8 was beginning to sway, or swoon me. The issue I eventually had with the Helix wasn't the lack of quality of the amp models, they were night and day improvements over the POD and HD series. There was still some fizziness in the top end, I call it digital artifacts, that I heard in the POD and HD series. Even with the improvements they made in the modeling, it was still there. This is ultimately what sold me on the AX8. If I was going to spend basically the same amount of money, I should get what I felt was the 'better' product.
I've had the AX8 for almost a year now and have not once felt I made a mistake or wondered if the Helix would be any better.