Certain fuzz pedals require the interaction with the guitar electronics to produce their characteristic results. A really quirky fuzz like a Fuzz Factory, with its controls for stability, gating, etc interacts with the guitar in unique ways and you can do fun stuff like tune the self oscillation with your tone knob. You don’t get those results with a buffer, and it’s probably not possible to model that either as your still going to have a buffer before the modeled circuit.
Other fuzz pedals sound different behind a buffer, but in a subjectively good way. I hands down like how my Buffalo Fx Patriot, a civil war muff, sounds with a buffer before it, such as a Boss pedal like the CS2. Changes how it responds, just like how a tube screamer or Blues Driver etc change how it sounds stacked.
Tube screamer with a Rat ? Cool boosted tones, and sadly two drive blocks don’t easily lend themselves to matching what is easy with two real pedals, though you can still have success stacking drives in the Axe.
Really though, if you are one of those folks who really love fuzz, your probably going to still want your collection of pedals. People who love germanium fuzz might own an analog man nkt275 white dot, a RCA, a Mullard oc44 etc, even though those are all the same circuit using different transitors. People who really love those things appreciate the different breakup etc, and it’s unlikely a model is going to satisfy, as part of it is probably just the emotional connection one may have with a collection of pedals on a shelf, especially fuzz, with the unique artwork, rare NOS parts that give bragging rights etc.
I think fuzz pedals are often as much about the collectibility as they are the tone. Pedals, while not cheap, are somewhat affordable, don’t take a bunch of space either. Most of us can’t really have a vintage amp collection, due to space, cost etc, but a shelf of fuzz pedals is a viable option.
Even if the Axe could perfectly model some of mine I think I’d still keep them. Some I built myself, some I’ve owned for decades, and I just kind of like plugging into a piece of hardware.
I don’t know, guess it makes me feel it makes my rig a little unique. If I was 100% in the box, then anyone else could match what I can do, and I’d be just another dude playing Axe into CLR. Great rig, but kind of generic too, know what I mean ?
Having some unique pedals in my chain, such as a really voltage starved Basic Audio Zippy, gives me tones I don’t think you can produce from the Axe, at least right now, and that is kind of cool, because people might hear a tone and think “what is that, how did he make that sound” and it’s a combination of a really weird fuzz circuit running into a great modeler with an advanced harmonizer and some sweet Plex delay. The Axe is a big part, but so is that few bucks of old parts wired up in a unique way. This is what makes pedals still pretty cool in my book