Which one should you buy?
Within a family these devices mostly share a sound engine, so the decision comes down to a handful of lines. These are those lines — and nothing else, because a table of things they all have in common buries the four that matter.
Which Helix should you buy?
Five full-size Line 6 modellers that share a sound engine and differ in chassis, connections and generation. These are the lines where they actually diverge.
Helix Stadium XL Floor · Helix Stadium Floor · Helix Floor · Helix Rack · Helix LT
Which small HX should you buy?
Four pedal-sized Line 6 boxes that share the effects library and differ in what else they carry. The first question is whether you want amp models at all.
HX Stomp XL · HX Stomp · HX Effects · HX One
Which Fractal should you buy?
Three current-generation Fractal devices and the previous one. Scenes and channels work the same on all of them; the grid, the amp count and the footswitches do not.
Axe-Fx III · FM9 · FM3 · Axe-Fx II