The distortion/overdrive models that are based on op amp/clipping diode circuits (e.g. Tube Screamer, Rat, Bluesbreaker, Klon, DS-1, Timmy) are incredible and indistinguishable from their hardware counterparts as far as I can tell. I've done a number of A/B tests with my own pedals and couldn't hear the difference after tweaking the knob positions. It's so good that I sold off all of my overlapping overdrive pedals. I'm not as happy with the fuzz models, either in the diversity of fuzz types or the detail/reality compared to my collection of fuzz pedals. In fairness to Fractal, at least some of that is due to the static input impedance of a modeler versus the dynamic input impedance of certain fuzz circuits. The relative lack of popularity of fuzz models vs everything else that the Axe does might also play a role—why expend resources overhauling a feature that isn't heavily used when you can focus on others that are heavily used? Anyway, if you're like most people and mostly use overdrive/distortion circuits, you'll love the current generation of drive models.
