If you’re in the former group, these kinds of devices are unlikely to fully satisfy you, at least when it comes to gigging and recording. So you might decide whether they are “worth it” based solely on their value as easy, light, and quiet practice platforms.
If you can’t tell (or don’t care about) the difference between the models and the real hardware, then these modeling sims start to look like a far better value. When individual amps can go for $1,500 to $2,000 or more, a massive gear collection like the one in the Quad Cortex mini is practically saving you money. You’d be a fool not to buy! (To paraphrase an explanation my son once gave me for a purchase he wanted to make.)
But even those in this group may not need an actual hardware pedal unless they really enjoy practicing without needing to use their regular computer—or unless they gig regularly. If you’re simply a recording guitarist who tends to work “in the box,” you might just pick up some cheaper Neural DSP plugins instead. Or you can buy a more comprehensive software suite like the new Paradise Guitar Studio from Universal Audio or one of the offerings from PolychromeDSP—all of which sound excellent.
If you’re content with software but want a free alternative, take a look at NAM, the Neural Amp Modeler. It’s open source modeling tech that also offers a community tone-sharing website and has been racking up lots of great reviews for its sound quality. (Though note that most of the NAM models are static captures; they sound great but represent only that exact setup and knob positioning, though the developers are working on more complex, adjustable models.)
All types of users can probably admit, though, that hardware and software modeling tech has made this a great time to be a guitar or bass player. Even if you don’t want to use them on a record, just being able to play around with and get to know this much gear with this much accuracy is a huge win for the home hobbyist and small-time gigging musician, who would otherwise never even set eyes on most of this stuff.
The key thing is just to get whatever works for you… and then to go forth and rock.