Over the years I have seen quite a bit of people even on this forum having issues with the Axe-Fx. In most cases it has been user error or a shitty output system or playing it at way too low volume for anything to sound good.
Fractal just puts controls at halfway on the amp block so that's as basic as it gets as a startup point and then you have to deliberately pick IRs rather than get them already paired like the Line6 Amp+Cab block does. Line6 sets a predefined sound for each block. That might be something that throws people off if it doesn't work with your guitars or output system. I often don't agree with their choices there but you can overwrite the defaults if you want. The stock cabs are probably the single biggest reason people struggle with the Helix. They are nowhere near as easy as Fractal's cab block that provides a big library of high quality IRs to choose from.
Fractal also has better stock presets so that can help people get started. I think these can be important factors for preferring a device. I have built my own presets for so long that I haven't even gone through the FM3 factory presets so for me it does not matter.
At one point I had the FM3, Quad Cortex and Helix Floor at the same time so I have mulled over the question. To me their amp modeling was not a big enough differentiator alone and it came to other factors. I really wanted to replace both FM3 and Helix with the QC but its effects were just too half-baked even though I loved the UI, form factor and capture functionality. So instead the QC got sold, I kept the FM3 and Helix and used them for different purposes. Helix for fx/routing/switching on my real amps and cabs, FM3 on the desk for direct recording, low volume use with headphones and travel because it's easier to pack up. I don't have much interest in the FM9 because it's much larger.
The FM3 was really an impulse purchase. I bought it used just so I could try the QC, Helix and FM3 all together and pick what I liked best and compare them on all fronts from amp to cab modeling to effects and usability. For me the key things were something like this:
- Quad Cortex. Best UI, form factor and onboard control. Capture feature is excellent. Limited effects, no computer editor. Needs time to grow with software updates.
- FM3. Best software feature set, best modulation and reverb effects, best computer editor. Lacking footswitching and worst onboard UI.
- Helix Floor. Best I/O, best usability on the floor (screen visibility, footswitching), good UI. Best compromise, but physically large.
I think you need to follow your heart and pick what you believe will work best for you. If you have struggled with the Helix too much to enjoy using it, then get something else. I sold my Axe-Fx 2 despite using it for years because I loathed operating it from the front panel and at the time the only alternative was the Axe-Fx 3 which was a lot more expensive and felt like only a half-step better for using it. I was already happy with the Axe-Fx 2 sound and available DSP. There's not a goldilocks device that would satisfy me in every aspect so you pick the things that are important for you.
