I took the Quad Cortex and had it sit right next to my Helix Floor. I plugged it into my computer and opened its software editor and also opened the software editor for the Helix. I will admit in comparing the two, the QC sounds more like an amp in front of you. The Helix has a little more processed sound though still sounding good. You get the presets and you need to tweak them with adding a compressor after the reverbs and doing some adjustments which will allow the Helix to get closer to the sounds of the QC. If I was just going to use a digital processor in my studio, I may consider getting the QC over the Helix. But for live use, the Helix for me, is a much better option. Here are my observations immediately before even hearing the QC.
1. There is no On/Off switch on the QC.
2. The power supply is a wall wart on the outside of the unit.
3. The power cable is thin and it lacks the ground third prong.
4. There is no ground lift button in the back. I found with the Marshall (1st preset) that I was getting a hum with my Les Paul. If I put my hand on the jack or strings, it would go away.
5. You can't see the Gig scene and the amp settings at the same time. Good luck with making changes to one of your settings without needing to swipe up on the screen, go into another view, make your adjustments, close that screen, and then swipe again to go back to the Gig Scene.
6. The 2nd row of buttons is lined up with the left side of the screen so its not centered properly. So hitting the wrong button could happen though I think you could get use to it.
7. The buttons are close together. Not as much of an issue on pushing the correct one L/R, but the back buttons and front buttons are also close to each other.
8. No expression pedal like the Helix, and the Helix Floor has a digital read out which makes it helpful if you want 85% of the pedal open.
9. Dynamic Control: With the Helix you can create an effect to go on only if you go past a certain volume. So if you put your volume on your guitar on 8 for rthy, by moving it to 10, you could have a overdrive pedal for more sustain for lead to kick in, or any other effect. I don't believe you can do that on the QC.
10. No Scribble strips. This makes my work flow on stage so much better.
I will say the editing software for the Helix looks more dated than the QC editing software. I think Line 6 can make some update to the screen. I like that the noise gate can be turned on before you even get to your first input of an amp or other effect on the QC. Hopefully with Yamaha behind Line 6 now, some of the plug ins and R&D support can help with a nice 4.0 update for the Helix. We don't need more amps and cabs but a better look and some work flow updates.
I will tell you though the Quad Cortex has some pros over the Helix Floor, there is just no way I would want to switch to a Quad Cortex. The Helix has just too many things that was done right over the QC.